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CHAPTER - 08
DATA FILE
Unit I
Programming and
Computational Thinking
(PCT-2)
(80 Theory + 70 Practical)
Prepared by
Praveen M Jigajinni
DCSc & Engg, PGDCA,ADCA,MCA.MSc(IT),Mtech(IT),MPhil (Comp. Sci)
Department of Computer Science, Sainik School Amaravathinagar
Cell No: 9431453730
Courtesy CBSE
Class
XII
LEARNING
OUTCOMES
LEARNING
OUTCOMES
After going through the chapter, student
will be able to:
Understand the importance of
data file for permanent storage of
data.
Understand how standard
Input/Output function work.
Distinguish between text and binary file
Open and close a file ( text and binary)
Read and write data in file
Write programs that manipulate data
INTRODUCTION – DATA
FILES
A file (i.e. data file) is a named
place on the disk where a sequence of
related data is stored.
In python files are simply
stream of data, so the structure of data
is not stored in the file, along with data.
BASIC OPERATIONS ON
FIL
E
Basic operations performed on a data file are:
1. Naming a file
2. Opening a file
3. Reading data from the file
4. Writing data in the file
5. Closing a file
BASIC OPERATIONS ON
FIL
E
FILE
PROCESSING
Contd..
Using these basic operations, we can
process file in many ways, such as
1. CREATING A FILE
2. TRAVERSING A FILE FOR DISPLAYING THE DATA ON
SCREEN
3. APPENDING DATAIN FILE
4. INSERTING DATAIN FILE
Contd.. next
FILE
PROCESSING
INTRODUCTION – DATA
FILES
5. DELETING DATAFROM FILE
6. CREATE A COPY OF FILE
7. UPDATING DATA IN THE FILE
…
etc
TYPES OF
FILES
TYPES OF
FILES
Python allow us to create and
manage two types of file
1. TEXT FILE
2. BINARY
FILE
What is Text File?
A text file is usually considered as
sequence of lines. Line is a sequence of
characters (ASCII or UNICODE), stored on
permanent storage media. The default
character coding in python is ASCII each
line is terminated by a special character,
known as End of Line (EOL). At the lowest
level, text file will be collection of bytes. Text
files are stored in human readable form and
they can also be created using any text
1. TEXT
FILE
What is Binary File?
A binaryfile contains arbitrarybinary
data
i.e. numbers storedin the file,
can be used for
numericaloperation(s).So when we
binary file, we have to interpret
the
work
o
n raw
bi
t
pattern(s) read from the file into correct type
of data in our program. In the case of binary
file it is extremely important that we
interpret the correct data type while reading
the file. Python provides special module(s)
for encoding and decoding of data for
2. BINARY
FILE
OPENING AND CLOSING
FILES
OPENING AND CLOSING
FILES
To handle data files in python, we
need to have a file object. Object can be
created by using open() function or file()
function.
To work on file, first thing we do is open
it. This is done by using built in function
open().
Syntax of open() function is
file_object = open(filename [, access_mode]
[,buffering])
OPENING AND CLOSING
FILES
open() requires three arguments to
work, first one ( filename ) is the
name of the file on secondary
storage media, which can be
string constant or a variable. The
name can include the description of
path, in case, the file does
not reside in the same folder /
directory in which we are working
The second parameter
(access_mode) describes how file will be
used throughout the program. This is an
OPENING AND CLOSING
FILES
The third parameter (buffering) is for
specifying how much is read from the file
in one read.
Finally, The function will return an
object of file type using which we will
manipulate the file, in our program.
When we work with file(s), a buffer (area in
memory where data is temporarily stored
before being written to file), is
automatically associated with file when we
open the file.
OPENING AND CLOSING
FILES
While writing the content in the file,
first it goes to buffer and once the buffer is
full, data is written to the file. Also when
file is closed, any unsaved data is
transferred to file. flush() function is used
to force transfer of data from buffer to file
FILE ACCESS
MODES
FILE ACCESS
MODES
MODE File Opens in
r Text File Read Mode
rb Binary File Read Mode
These are the default modes. The file
pointer is placed at the beginning for
reading purpose, when we open a file in
this mode.
FILE ACCESS
MODES
MOD
E
File Opens
in
r+ Text File Read & Write Mode
rb+ Binary File Read Write
Mode w Text file write mode
wb Text and Binary File Write
Mode w+ Text File Read and
Write Mode
wb+ Text and Binary File Read and Write
Mode
a Appends text file at the end of file,
if file does not exists it creates the
file.
FILE ACCESS
MODES
MOD
E
File Opens
in
ab Appends both text and binary files at
the end of file, if file does not exists
it creates the file.
a+ Text file appending and reading.
ab+ Text and Binary file for appending
and reading.
FILE ACCESS MODES -
EXAMPLE
For Ex:
f=open(“notes.txt”, ‘r’)
Thisis the defaultmodefor
a
file.
notes.txtis a text file and
is opened in read
mode only.
FILE ACCESS MODES -
EXAMPLE
For Ex:
f=open(“notes.txt”,‘r+’)
notes.txt is a text file and is
opened in read and write
mode.
FILE ACCESS MODES -
EXAMPLE
For Ex:
f=open(“tests.dat ”, ‘rb’)
tests.dat is a binary file
and
is opened in read only mode.
FILE ACCESS MODES -
EXAMPLE
For Ex:
f=open(“tests.dat”, ‘rb+’)
tests.dat is binary file and
is opened in both modes that is
reading and writing.
FILE ACCESS MODES -
EXAMPLE
For Ex:
f=open(“tests.dat”, ‘ab+’)
tests.dat is binary file and
is opened in both modes that is
reading and appending.
close
FUNCTION
close
FUNCTION
fileobject. close() will be used to
close the file object, once we have
finished working on it. The method will
free up all the system resources used by
the file, this means that once file is
closed, we will not be able to use the file
object any more.
For example:
f.close()
FILE READING
METHODS
FILE READING
METHODS
PYTHO
N
PROGRA
M
A Program reads a
text/binary file from
FILE READING
METHODS
Followings are the methods
to read a data
from the file.
1. readline()METHOD
2. readlines() METHOD
3. read() METHOD
readline()
METHO
D
readline() will return a line read, as a
string from the file. First call to function
will return first line, second call next line
and so on.
It's syntax is,
fileobject.readline()
readline()
EXAMP
LE
First create a text file and save
under filename notes.txt
readline()
EXAMP
LE
readline()EXAMPLE
O/P
readline() will return only one line
from a file, but notes.txt file containing
three lines of text
readlines()
METHO
D
readlines()can be used to read the
entire content of the file. You need to be
careful while using it w.r.t. size of memory
required before using the function. The
method will return a list of strings, each
separated by n. An example of reading
entire data of file in list is:
It's syntax is,
fileobject.readlines()
as it returns a list, which can then be
used for manipulation.
readlines()
EXAMP
LE
readlines()
EXAMP
LE
The readlines() method will return
a list of strings, each separated by n
read()
METHO
D
The read() method is used to read
entire
file
The syntax is:
fileobject.read()
For example
Contd
…
read() METHOD
EXAMPLE
read() METHOD EXAMPLE
O/P
The read() method will return
entire
file.
read(size)
METHO
D
read(size)
METHO
D
read() can be used to read specific
size string from file. This function also
returns a string read from the file.
Syntax of read() function is:
fileobject.read([siz
e]) For Example:
f.read(1) will read
single byte or character from a file.
read(size) METHOD
EXAMPLE
byte or character
from
f.read(1) will read
single a file and
assigns to x.
read(size) METHOD
EXAMPLE O/P
WRITING IN TO
FILE
WRITING
METHODS
PYTHO
N
PROGRA
M
A Program writesinto a
text/binary file from hard disk.
WRITING
METHODS
1. write () METHOD
2. writelines()
METHOD
1. write ()
METHOD
For sending data in file, i.e. to
create / write in the file, write() and
writelines() methods can be used.
write() method takes a string ( as
parameter ) and writes it in the file.
For storing data with end of line
character, you will have to add n
character to end of the string
1. write () METHOD
EXAMPLE
Use ‘a’ in open function to append
or add the information to the file. ‘a+’ to
add as well as read the file.
1. write () METHOD
EXAMPLE
if you execute the program n times,
the file is opened in w mode meaning it
deletes content of file and writes fresh
every time you run.
1. write () METHOD EXAMPLE
O/P
if you execute the program n times,
the file is opened in w mode meaning it
deletes content of file and writes fresh
every time you run.
1. write () METHOD
EXAMPLE
2
now content of test1.txt is changed
because the file is opened in w mode and
this mode deletes all content and writes
fresh if file exists. n write to next line. If
not used it writes on the same line.
1. write () METHOD
EXAMPLE
2
So test1.txt is already exists in
harddisk and it deletes all content and
writes fresh. If file not found it creates
new file.
1. write () METHOD
EXAMPLE
2
So test1.txt is already exists in
harddisk and it deletes all content and
writes fresh. If file not found it creates
new file.
2. writelines()
METHOD
For writing a string at a time, we use
write() method, it can't be used for writing
a list, tuple etc. into a file.
Sequence data type can be written
using writelines() method in the file. It's
not that, we can't write a string using
writelines() method.
It's syntax is:
fileobject.writelines(seq)
2. writelines()
METHOD
So, whenever we have to write a
sequence of string / data type, we will
use writelines(), instead of write().
Example:
f = open('test2.txt','w')
str = 'hello world.n this is my first
file handling program.n I am
using python language"
f.writelines(st
r) f.close()
RANDOM ACCESS
METHODS
RANDOM ACCESS
METHODS
All reading and writing functions
discussed till now, work sequentially in
the file. To access the contents of file
randomly – following methods are use.
seek
method
tell
seek()method can be used to
position the file object at particular place
in the file.
It's syntax is :
fileobject.seek(offset [, from_what])
here offset is used to calculate the
position of fileobject in the file in bytes.
Offset is added to from_what (reference
point) to get the position. Following is the
list of from_what values:
seek
method
Value reference
point
0
1
2
beginning of the
file current
position of file end
of file
defaultvalueof from_what is 0, i.e.
beginning of the file.
seek
method
seek
method
f.seek(7) keepsfile pointer at readsthe
file content from 8th position
onwards to till EOF.
seek
method
Results: - So 8th position onwards to
till EOF.
Reading according to
size
In the input function if you specify
the number of bytes that many number of
bytes can be fetched and assigned to an
identifier.
Reading according to
size
f.read(1) will read single byte/
character starting from byte number 8.
hence byte number 8 is P so one
character/byte is fetched and assigned to
f_data identifier.
Reading according to
size
will read 2
chars/bytes will
read 4 chars/bytes
f.read(2)-
f.read(4) -
and so
on..
tell() method returns an integer
giving the current position of object in
the file. The integer returned specifies
the number of bytes from the beginning
of the file till the current position of file
object.
It's syntax is
fileobject.tell()
tell
method
tell()
method
tell()
metho
d
tell() method returns an integer and
assigned to pos variable. It is the
current position from the beginning of
file.
BINARY
FILES
CREATING BINARY
FILES
CREATING BINARY
FILES
SEEING CONTENT OF
BINARY FILE
CONTENT OF BINARY
FILE
Content of binary file which is in
codes.
READING BINARY FILES TROUGH
PROGRAM
READING BINARY FILE
PROGRAM
READING BINARY FILE
PROGRAM
CONTENT OF BINARY
FILE
PICKELING AND
UNPICKLING
USING PICKEL
MODULE
PICKELING AND
UNPICKLING
USING PICKEL
MODULE
Use the python module pickle for
structured data such as list or
directory to a file.
PICKLING refers to the process
of converting the structure to a byte
stream before writing to a file.
while reading the contents of the
file, a reverse process called
UNPICKLING is used to convert the
byte stream back to the original
structure.
PICKELING AND
UNPICKLING
USING PICKEL
MODULE
Firstwe needto importthe module,It
provides two main methods for the
purpose:-
1) dump() method
2) load() method
pickle.dump()
Method
Use pickle.dump() method to write
the object in file which is opened in
binary access mode.
Syntax of dump method is:
dump(object,fileobject)
pickle.dump()
Method
pickle.dump()
Method
# A program to write list
sequence in a binary file
pickle.dump()
Method
OUTPU
T
pickle.dump()
Method
list.dat file
in
Once you try to
open python
editor to see the
conte
nt
pytho
n
generates decoding
error.
pickle.load()
Method
pickle.load()
Method
pickle.load() method is used to read
the binary file.
pickle.load()
Method
pickle.load() method is used to read
the binary file.
DIFFERENCE BETWEEN TEXT
FILES AND BINARY
FILES
DIFFERENCE BETWEEN TEXT FILESAND
BINARY FILES
DIFFERENCE BETWEEN TEXT FILESAND
BINARY FILES
Text Files
1.Text Files
are
sequential
files
2.Text files only
stores texts
3. There is a
delimiter EOL (End
of Line i.e n)
Binary Files
1. A Binary file
contain arbitrary
binary data
2 Binary Files are
used to store
binary data such
as image, video,
audio, text
3. There is no
delimiter
DIFFERENCE BETWEEN TEXT FILESAND
BINARY FILES
Text Files Binary Files
4. Due to delimiter
text files takes more
time to process.
while reading or
writing operations
are performed on
file.
4. No presence of
delimiter makes
files to process fast
while reading or
writing operations
are performed on
file.
5. Text files
easy to
understand
because these
files are in human
5. Binary files are
difficult to
understand.
DIFFERENCE BETWEEN TEXT FILESAND
BINARY FILES
Text Files
6.Text files are
having extension
.txt
7.Programming on
text files are very
easy.
Binary Files
6.Binary files are
having .dat
extension
7.Programming on
binary files are
difficult.
DIFFERENCE BETWEEN TEXT
FILES AND BINARY
FILES
TEXT
FILE
1.
Bit
s
characte
r.
BINARY FILE
represent1. Bits represent
a
custom
data.
2.
Les
s
corrup
t
prone to get 2. Can
easily get as changes
corrupted, even a single
reflect as soon as the bit
change maycorrupt file is
opened and can the file.
easily be undone
DIFFERENCE BETWEEN TEXT
FILES AND BINARY
FILES
TEXT FILE BINARY FILE
3. Canstoreonly plain 3. Can store
text in a file. types of
data
differen
t
(imag
e,
audio,text) in a
single file.
4.
Widel
y
format and
opened
using
simple text
editor.
used file 4. Developed
especially can
be for an application
and any may not be
understood
by other
applications.
DIFFERENCE BETWEEN TEXT
FILES AND BINARY
FILES
TEXT FILE BINARY FILE
5. Mostly .txt and .rtf
are used as
extensions to text
files.
5. Can have any
application defined
extension.
PYTHON FILE OBJECT
ATTRIBUTES
PYTHON FILE OBJECT
ATTRIBUTES
File attributes give information
about the file and file state.
Attribute Function
name Returns the name of the file
closed
Returns true if file is closed.
False otherwise.
mode The mode in which file is open.
softspace
Returns a Boolean that
indicates whether a space
character needs to
be printed before another
value when using the print
OTHER METHODS OF
FILEOBJECT
OTHER METHODS OF
FILEOBJECT
Method Function
readable()
Returns True/False whether file is
readable
writable()
Returns True/False whether file is
writable
fileno()
Return the Integer descriptor used
by
Python to request I/O operations
from Operating System
flush() Clears the internal buffer for the
file.
OTHER METHODS OF
FILEOBJECT
Method Function
isatty()
Returns True if file is connected to
a
Tele-TYpewriter (TTY)
device or something
similar.
truncate([size) Truncate the file, up to specified
bytes.
next(iterator,[d
ef ault])
Iterate over a file when file is used
as an
HANDLING FILES
THROUGH OS
MODULE
HANDLING FILES
THROUGH OS
MODULE
The os module of Python allows you
to perform Operating System dependent
operations such as making a folder,
listing contents of a folder, know about a
process, end a process etc..
Let's see some useful os module
methods that can help you to handle files
and folders in your program.
ABSOLUTE PATH AND
RELATIVE PATH
ABSOLUTE
PATH
Absolute path of file is file location,
where in it starts from the top most
directory
ABSOLUTE
PATH
RELATIVE
PATH
Relative Path of file is file location,
where in it starts from the current working
directory
Myfoldermyfile.txt
RELATIVE
PATH
HANDLING FILES
THROUGH OS
MODULE
Method Function
os.makedirs() Create a new folder
os.listdir() List the contents of a folder
os.getcwd() Show current working
directory
os.path.getsize()
show file size in bytes
of file passed
in parameter
os.path.isfile() Is passed parameter a file
os.path.isdir() Is passed parameter a folder
os.chdir Change directory/folder
HANDLING FILES
THROUGH OS
MODULE
Method Function
os.rename(current,new
)
Rename a file
os.remove(file_name) Delete a file
PROGRA
MS
PROGRA
MS
1. Write a function to create a text file
containing following data
Neitherapplenor pine are in pineapple.
Boxing rings are square.
Writers write, but fingers don't fing.
Overlook and oversee are opposites. A
house can burn up as it burns down. An
alarm goes off by going on.
PROGRA
MS
2. Read back the entire file content using
read() or readlines () and display on
screen.
3.Append more text of your choice in the
file and display the content of file with line
numbers prefixed to line.
4. Display last line of file.
Contd
PROGRA
MS
firs
t
lin
e
fro
m
10t
h
charact
er
5.
Displa
y onwards
6. Readand display a line from the
file. Ask user to provide the line
number to be read.
PROGRA
MS
7. A text file named MATTER.TXT contains
some text, which needs to be displayed
such that every next character is
separated by a symbol ‘#’.
8. Write a statement in Python to open a
text file STORY.TXT so that new
contents can be added at the end of it.
PROGRA
MS
9. Write a method in Python to read lines
from a text file INDIA.TXT, to find and
display the occurrence of the word
‘‘India’’.
For example :
If the content of the file is
‘‘India is the fastest growing economy.
India is looking for more investments around the
globe. The whole world is looking at India as a
great market.
Most of the Indians can foresee the heights that
India is capable of reaching.’’
PROGRA
MS
10. Write a function to count total number of
spaces, lines and characters in a given line
of text
PROGRA
MS
11. Write a function to count total number of
digits in a given line of text
PROGRA
MS
12. Write a function to copy the content of
notes.txt to sub.txt
NOTES.txt FILE
PROGRA
MS
12. Write a function to copy the content of
notes.txt to sub.txt
PROGRAM -
OUTPUT
12. Write a function to copy the content of
notes.txt to sub.txt
SUB.txt FILE
PROGRAM -
OUTPUT
13. Write a function to append or add a line of
text in notes.txt
NOTES.txt FILE
PROGRA
MS
13. Write a function to append or add a line of
text in notes.txt
PROGRAM -
OUTPUT
13. Write a function to append or add a line of
text in notes.txt
PROGRA
MS
14. Write a function to display total number of
lines in a notes.txt file.
NOTES.txt
FILE
PROGRA
MS
14. Write a function to display total number of
lines in a notes.txt file.
NOTES.txt
FILE
PROGRA
MS
14. Write a function to display total number of
lines in a notes.txt file.
PROGRAM -
OUTPUT
14. Write a function to display total number of
lines in a notes.txt file.
OUTPU
T
PROGRA
MS
ANTOHER METHOD
14. Write a function in pythonto
countthe total number of lines in a
file ‘Mem.txt’
PROGRA
MS
14. Write a function in pythonto
countthe total number of lines in a
file ‘Mem.txt’
‘Mem.txt’ file contains
PROGRA
MS
14. Write a function in pythonto
countthe total number of lines in a
file ‘Mem.txt’
PROGRA
MS
15. Writea function to display last
line of notes.txt file.
NOTES.txt
FILE
PROGRA
MS
15. Writea function to display last
line of notes.txt file.
PROGRAM -
OUTPUT
OUTPU
T
15. Writea function to display last
line of notes.txt file.
PROGRA
MS
16. Write a function COUNT_DO( ) in
Python to count the presence of a word
‘do’ in a text file “MEMO.TXT”.
Example :
is
a
s
If the content of the file
“MEMO.TXT” follows:
I will do it, if you request me to
do it. It would have been done
much earlier. ) will display
the
The function
COUNT_DO(
following message:
Count of -do- in flie:
PROGRA
MS
17. Write a function in Python to count the
no. of “Me” or “My” words present in a
text file “DIARY.TXT”.
If the file “DIARY.TXT” content is as follows
:
My first book was Me and My family. It gave
me chance to be known to the world.
The output of the function should be
Count of Me/ My in file :
PROGRA
MS
18. Write a function in Python to count and
display the number of lines starting with
alphabet ‘A’ present in a text file
“LINES.TXT”.
Example: If the file “LINES.TXT”
contains the following lines,
A boy is playing
there. There is a
playground.
An aeroplane is in the sky.
Alphabets and numbers are allowed
in the password.
PROGRA
MS
19. Write a function in Python to read the
content of a text file “DELHI.TXT” and
display all those lines on screen, which
are Either starting with ‘D’ or starting with
‘M’.
DELHI.TXT
File
PROGRA
MS
PROGRA
MS
20. Write a function in Python to count the
number of alphabets present in a text file
“NOTES.TXT”.
NOTES.TXT FILE
PROGRA
MS
20. Write a function in Python to count the
number of alphabets present in a text file
“NOTES.TXT”.
NOTES.TXT FILE
CBSE QUESTION PAPER
QNO 4
CBSE QUESTION PAPER
2015 Delhi
CBSE QUESTION PAPER
2015 Delhi
4(a) Differentiate between the following :
1
(i) f = open(‘diary.txt’, ‘r’)
(ii)f = open(‘diary.txt’, ‘w’)
4(b) Write a method in python to read the
content from a text file diary.txt line by
line and display the same on screen. 2
CBSE QUESTION PAPER
2016 Delhi
CBSE QUESTION PAPER
2016 Delhi
4. (a) Write a statement in Python to
perform the following operations : 1
 To open a text file “BOOK.TXT” in read
mode
To open a text file “BOOK.TXT” in
write mode
4(b) Write a method in python to read the
content from a text file diary.txt line by
line and display the same on screen. 2
CBSE QUESTION PAPER
2017 Delhi
CBSE QUESTION PAPER
2017 Delhi
4 (a) Differentiate between file modes r+
and rb+ with respect to Python. 1
4(b) Write a method in Python to read
lines from a text file MYNOTES.TXT,
and display those lines, which are
starting with the alphabet K 2
CBSE QUESTION PAPER
2018 AI
CBSE QUESTION PAPER
2018 AI
4 (a) Write a statement in Python to open a
text file STORY.TXT so that new contents
can be added at the end of it. 1
4 (b) Write a method in Python to read lines
from a text file INDIA.TXT, to find and
display the 2
occurrence of the word
‘‘India’’.
For example :
If the content of the file is
‘‘India is the fastest growing
CBSE QUESTION PAPER
2018 AI
India is looking for more investments
around the globe.
The whole world is looking at India as a
great market.
Most of the Indians can foresee the
heights that India is capable of
reaching.’’
The output should be 4. 2
ADDITIONAL
PROGRAMS
ADDITIONAL
PROGRAMS
1. Write a Python program to read an
entire text file.
2. Write a Python program to read first n
lines of a file.
3. Write a Python program to append
text to a file and display the text.
4. Write a Python program to read last n
lines of a file.
5. Write a Python program to read last n
lines of a file.
1. Write a Python program to read a file
line by line and store it into a list.
2. Write a Python program to read a file
line by line store it into a variable.
3. Write a Python program to read a file
line by line store it into an array.
4. Write a python program to find the
longest words.
5. Write a Python program to count the
number of lines in a text file.
6. Write a Python program to
count the frequency of words
in a file.
ADDITIONAL
PROGRAMS
5. Write a Python program to read a file
line by line and store it into a list.
6. Write a Python program to read a file
line by line store it into a variable.
7. Write a Python program to read a file
line by line store it into an array.
8. Write a python program to find the
longest words.
9. Write a Python program to count the
number of lines in a text file.
10.Write a Python program to
count the frequency of words
in a file.
ADDITIONAL
PROGRAMS
CLASS
TEST
1.Write a program to count total no of
spaces,words,characters,lines in a
msg.txt file.
2.What is file?
3.Differentiate between text files and binary
files. 4.Write a program to copy the content
of notes.txt from 3rd character to till end of
file to para.txt
5. Write a program to create binary file
Time: 40 Min
Max Marks:
40
Class : XII
Topic: FILE HANDLING
Each Question carries 4
Marks
Thank You

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DFH PDF-converted.pptx

  • 2. Unit I Programming and Computational Thinking (PCT-2) (80 Theory + 70 Practical) Prepared by Praveen M Jigajinni DCSc & Engg, PGDCA,ADCA,MCA.MSc(IT),Mtech(IT),MPhil (Comp. Sci) Department of Computer Science, Sainik School Amaravathinagar Cell No: 9431453730 Courtesy CBSE Class XII
  • 4. LEARNING OUTCOMES After going through the chapter, student will be able to: Understand the importance of data file for permanent storage of data. Understand how standard Input/Output function work. Distinguish between text and binary file Open and close a file ( text and binary) Read and write data in file Write programs that manipulate data
  • 5. INTRODUCTION – DATA FILES A file (i.e. data file) is a named place on the disk where a sequence of related data is stored. In python files are simply stream of data, so the structure of data is not stored in the file, along with data.
  • 7. Basic operations performed on a data file are: 1. Naming a file 2. Opening a file 3. Reading data from the file 4. Writing data in the file 5. Closing a file BASIC OPERATIONS ON FIL E
  • 9. Using these basic operations, we can process file in many ways, such as 1. CREATING A FILE 2. TRAVERSING A FILE FOR DISPLAYING THE DATA ON SCREEN 3. APPENDING DATAIN FILE 4. INSERTING DATAIN FILE Contd.. next FILE PROCESSING
  • 10. INTRODUCTION – DATA FILES 5. DELETING DATAFROM FILE 6. CREATE A COPY OF FILE 7. UPDATING DATA IN THE FILE … etc
  • 12. TYPES OF FILES Python allow us to create and manage two types of file 1. TEXT FILE 2. BINARY FILE
  • 13. What is Text File? A text file is usually considered as sequence of lines. Line is a sequence of characters (ASCII or UNICODE), stored on permanent storage media. The default character coding in python is ASCII each line is terminated by a special character, known as End of Line (EOL). At the lowest level, text file will be collection of bytes. Text files are stored in human readable form and they can also be created using any text 1. TEXT FILE
  • 14. What is Binary File? A binaryfile contains arbitrarybinary data i.e. numbers storedin the file, can be used for numericaloperation(s).So when we binary file, we have to interpret the work o n raw bi t pattern(s) read from the file into correct type of data in our program. In the case of binary file it is extremely important that we interpret the correct data type while reading the file. Python provides special module(s) for encoding and decoding of data for 2. BINARY FILE
  • 16. OPENING AND CLOSING FILES To handle data files in python, we need to have a file object. Object can be created by using open() function or file() function. To work on file, first thing we do is open it. This is done by using built in function open(). Syntax of open() function is file_object = open(filename [, access_mode] [,buffering])
  • 17. OPENING AND CLOSING FILES open() requires three arguments to work, first one ( filename ) is the name of the file on secondary storage media, which can be string constant or a variable. The name can include the description of path, in case, the file does not reside in the same folder / directory in which we are working The second parameter (access_mode) describes how file will be used throughout the program. This is an
  • 18. OPENING AND CLOSING FILES The third parameter (buffering) is for specifying how much is read from the file in one read. Finally, The function will return an object of file type using which we will manipulate the file, in our program. When we work with file(s), a buffer (area in memory where data is temporarily stored before being written to file), is automatically associated with file when we open the file.
  • 19. OPENING AND CLOSING FILES While writing the content in the file, first it goes to buffer and once the buffer is full, data is written to the file. Also when file is closed, any unsaved data is transferred to file. flush() function is used to force transfer of data from buffer to file
  • 21. FILE ACCESS MODES MODE File Opens in r Text File Read Mode rb Binary File Read Mode These are the default modes. The file pointer is placed at the beginning for reading purpose, when we open a file in this mode.
  • 22. FILE ACCESS MODES MOD E File Opens in r+ Text File Read & Write Mode rb+ Binary File Read Write Mode w Text file write mode wb Text and Binary File Write Mode w+ Text File Read and Write Mode wb+ Text and Binary File Read and Write Mode a Appends text file at the end of file, if file does not exists it creates the file.
  • 23. FILE ACCESS MODES MOD E File Opens in ab Appends both text and binary files at the end of file, if file does not exists it creates the file. a+ Text file appending and reading. ab+ Text and Binary file for appending and reading.
  • 24. FILE ACCESS MODES - EXAMPLE For Ex: f=open(“notes.txt”, ‘r’) Thisis the defaultmodefor a file. notes.txtis a text file and is opened in read mode only.
  • 25. FILE ACCESS MODES - EXAMPLE For Ex: f=open(“notes.txt”,‘r+’) notes.txt is a text file and is opened in read and write mode.
  • 26. FILE ACCESS MODES - EXAMPLE For Ex: f=open(“tests.dat ”, ‘rb’) tests.dat is a binary file and is opened in read only mode.
  • 27. FILE ACCESS MODES - EXAMPLE For Ex: f=open(“tests.dat”, ‘rb+’) tests.dat is binary file and is opened in both modes that is reading and writing.
  • 28. FILE ACCESS MODES - EXAMPLE For Ex: f=open(“tests.dat”, ‘ab+’) tests.dat is binary file and is opened in both modes that is reading and appending.
  • 30. close FUNCTION fileobject. close() will be used to close the file object, once we have finished working on it. The method will free up all the system resources used by the file, this means that once file is closed, we will not be able to use the file object any more. For example: f.close()
  • 32. FILE READING METHODS PYTHO N PROGRA M A Program reads a text/binary file from
  • 33. FILE READING METHODS Followings are the methods to read a data from the file. 1. readline()METHOD 2. readlines() METHOD 3. read() METHOD
  • 34. readline() METHO D readline() will return a line read, as a string from the file. First call to function will return first line, second call next line and so on. It's syntax is, fileobject.readline()
  • 35. readline() EXAMP LE First create a text file and save under filename notes.txt
  • 37. readline()EXAMPLE O/P readline() will return only one line from a file, but notes.txt file containing three lines of text
  • 38. readlines() METHO D readlines()can be used to read the entire content of the file. You need to be careful while using it w.r.t. size of memory required before using the function. The method will return a list of strings, each separated by n. An example of reading entire data of file in list is: It's syntax is, fileobject.readlines() as it returns a list, which can then be used for manipulation.
  • 40. readlines() EXAMP LE The readlines() method will return a list of strings, each separated by n
  • 41. read() METHO D The read() method is used to read entire file The syntax is: fileobject.read() For example Contd …
  • 43. read() METHOD EXAMPLE O/P The read() method will return entire file.
  • 45. read(size) METHO D read() can be used to read specific size string from file. This function also returns a string read from the file. Syntax of read() function is: fileobject.read([siz e]) For Example: f.read(1) will read single byte or character from a file.
  • 46. read(size) METHOD EXAMPLE byte or character from f.read(1) will read single a file and assigns to x.
  • 49. WRITING METHODS PYTHO N PROGRA M A Program writesinto a text/binary file from hard disk.
  • 50. WRITING METHODS 1. write () METHOD 2. writelines() METHOD
  • 51. 1. write () METHOD For sending data in file, i.e. to create / write in the file, write() and writelines() methods can be used. write() method takes a string ( as parameter ) and writes it in the file. For storing data with end of line character, you will have to add n character to end of the string
  • 52. 1. write () METHOD EXAMPLE Use ‘a’ in open function to append or add the information to the file. ‘a+’ to add as well as read the file.
  • 53. 1. write () METHOD EXAMPLE if you execute the program n times, the file is opened in w mode meaning it deletes content of file and writes fresh every time you run.
  • 54. 1. write () METHOD EXAMPLE O/P if you execute the program n times, the file is opened in w mode meaning it deletes content of file and writes fresh every time you run.
  • 55. 1. write () METHOD EXAMPLE 2 now content of test1.txt is changed because the file is opened in w mode and this mode deletes all content and writes fresh if file exists. n write to next line. If not used it writes on the same line.
  • 56. 1. write () METHOD EXAMPLE 2 So test1.txt is already exists in harddisk and it deletes all content and writes fresh. If file not found it creates new file.
  • 57. 1. write () METHOD EXAMPLE 2 So test1.txt is already exists in harddisk and it deletes all content and writes fresh. If file not found it creates new file.
  • 58. 2. writelines() METHOD For writing a string at a time, we use write() method, it can't be used for writing a list, tuple etc. into a file. Sequence data type can be written using writelines() method in the file. It's not that, we can't write a string using writelines() method. It's syntax is: fileobject.writelines(seq)
  • 59. 2. writelines() METHOD So, whenever we have to write a sequence of string / data type, we will use writelines(), instead of write(). Example: f = open('test2.txt','w') str = 'hello world.n this is my first file handling program.n I am using python language" f.writelines(st r) f.close()
  • 61. RANDOM ACCESS METHODS All reading and writing functions discussed till now, work sequentially in the file. To access the contents of file randomly – following methods are use. seek method tell
  • 62. seek()method can be used to position the file object at particular place in the file. It's syntax is : fileobject.seek(offset [, from_what]) here offset is used to calculate the position of fileobject in the file in bytes. Offset is added to from_what (reference point) to get the position. Following is the list of from_what values: seek method
  • 63. Value reference point 0 1 2 beginning of the file current position of file end of file defaultvalueof from_what is 0, i.e. beginning of the file. seek method
  • 64. seek method f.seek(7) keepsfile pointer at readsthe file content from 8th position onwards to till EOF.
  • 65. seek method Results: - So 8th position onwards to till EOF.
  • 66. Reading according to size In the input function if you specify the number of bytes that many number of bytes can be fetched and assigned to an identifier.
  • 67. Reading according to size f.read(1) will read single byte/ character starting from byte number 8. hence byte number 8 is P so one character/byte is fetched and assigned to f_data identifier.
  • 68. Reading according to size will read 2 chars/bytes will read 4 chars/bytes f.read(2)- f.read(4) - and so on..
  • 69. tell() method returns an integer giving the current position of object in the file. The integer returned specifies the number of bytes from the beginning of the file till the current position of file object. It's syntax is fileobject.tell() tell method
  • 71. tell() metho d tell() method returns an integer and assigned to pos variable. It is the current position from the beginning of file.
  • 76. CONTENT OF BINARY FILE Content of binary file which is in codes.
  • 77. READING BINARY FILES TROUGH PROGRAM
  • 82. PICKELING AND UNPICKLING USING PICKEL MODULE Use the python module pickle for structured data such as list or directory to a file. PICKLING refers to the process of converting the structure to a byte stream before writing to a file. while reading the contents of the file, a reverse process called UNPICKLING is used to convert the byte stream back to the original structure.
  • 83. PICKELING AND UNPICKLING USING PICKEL MODULE Firstwe needto importthe module,It provides two main methods for the purpose:- 1) dump() method 2) load() method
  • 84. pickle.dump() Method Use pickle.dump() method to write the object in file which is opened in binary access mode. Syntax of dump method is: dump(object,fileobject)
  • 86. pickle.dump() Method # A program to write list sequence in a binary file
  • 88. pickle.dump() Method list.dat file in Once you try to open python editor to see the conte nt pytho n generates decoding error.
  • 90. pickle.load() Method pickle.load() method is used to read the binary file.
  • 91. pickle.load() Method pickle.load() method is used to read the binary file.
  • 92. DIFFERENCE BETWEEN TEXT FILES AND BINARY FILES
  • 93. DIFFERENCE BETWEEN TEXT FILESAND BINARY FILES
  • 94. DIFFERENCE BETWEEN TEXT FILESAND BINARY FILES Text Files 1.Text Files are sequential files 2.Text files only stores texts 3. There is a delimiter EOL (End of Line i.e n) Binary Files 1. A Binary file contain arbitrary binary data 2 Binary Files are used to store binary data such as image, video, audio, text 3. There is no delimiter
  • 95. DIFFERENCE BETWEEN TEXT FILESAND BINARY FILES Text Files Binary Files 4. Due to delimiter text files takes more time to process. while reading or writing operations are performed on file. 4. No presence of delimiter makes files to process fast while reading or writing operations are performed on file. 5. Text files easy to understand because these files are in human 5. Binary files are difficult to understand.
  • 96. DIFFERENCE BETWEEN TEXT FILESAND BINARY FILES Text Files 6.Text files are having extension .txt 7.Programming on text files are very easy. Binary Files 6.Binary files are having .dat extension 7.Programming on binary files are difficult.
  • 97. DIFFERENCE BETWEEN TEXT FILES AND BINARY FILES TEXT FILE 1. Bit s characte r. BINARY FILE represent1. Bits represent a custom data. 2. Les s corrup t prone to get 2. Can easily get as changes corrupted, even a single reflect as soon as the bit change maycorrupt file is opened and can the file. easily be undone
  • 98. DIFFERENCE BETWEEN TEXT FILES AND BINARY FILES TEXT FILE BINARY FILE 3. Canstoreonly plain 3. Can store text in a file. types of data differen t (imag e, audio,text) in a single file. 4. Widel y format and opened using simple text editor. used file 4. Developed especially can be for an application and any may not be understood by other applications.
  • 99. DIFFERENCE BETWEEN TEXT FILES AND BINARY FILES TEXT FILE BINARY FILE 5. Mostly .txt and .rtf are used as extensions to text files. 5. Can have any application defined extension.
  • 101. PYTHON FILE OBJECT ATTRIBUTES File attributes give information about the file and file state. Attribute Function name Returns the name of the file closed Returns true if file is closed. False otherwise. mode The mode in which file is open. softspace Returns a Boolean that indicates whether a space character needs to be printed before another value when using the print
  • 103. OTHER METHODS OF FILEOBJECT Method Function readable() Returns True/False whether file is readable writable() Returns True/False whether file is writable fileno() Return the Integer descriptor used by Python to request I/O operations from Operating System flush() Clears the internal buffer for the file.
  • 104. OTHER METHODS OF FILEOBJECT Method Function isatty() Returns True if file is connected to a Tele-TYpewriter (TTY) device or something similar. truncate([size) Truncate the file, up to specified bytes. next(iterator,[d ef ault]) Iterate over a file when file is used as an
  • 106. HANDLING FILES THROUGH OS MODULE The os module of Python allows you to perform Operating System dependent operations such as making a folder, listing contents of a folder, know about a process, end a process etc.. Let's see some useful os module methods that can help you to handle files and folders in your program.
  • 108. ABSOLUTE PATH Absolute path of file is file location, where in it starts from the top most directory ABSOLUTE PATH
  • 109. RELATIVE PATH Relative Path of file is file location, where in it starts from the current working directory Myfoldermyfile.txt RELATIVE PATH
  • 110. HANDLING FILES THROUGH OS MODULE Method Function os.makedirs() Create a new folder os.listdir() List the contents of a folder os.getcwd() Show current working directory os.path.getsize() show file size in bytes of file passed in parameter os.path.isfile() Is passed parameter a file os.path.isdir() Is passed parameter a folder os.chdir Change directory/folder
  • 111. HANDLING FILES THROUGH OS MODULE Method Function os.rename(current,new ) Rename a file os.remove(file_name) Delete a file
  • 113. PROGRA MS 1. Write a function to create a text file containing following data Neitherapplenor pine are in pineapple. Boxing rings are square. Writers write, but fingers don't fing. Overlook and oversee are opposites. A house can burn up as it burns down. An alarm goes off by going on.
  • 114. PROGRA MS 2. Read back the entire file content using read() or readlines () and display on screen. 3.Append more text of your choice in the file and display the content of file with line numbers prefixed to line. 4. Display last line of file. Contd
  • 115. PROGRA MS firs t lin e fro m 10t h charact er 5. Displa y onwards 6. Readand display a line from the file. Ask user to provide the line number to be read.
  • 116. PROGRA MS 7. A text file named MATTER.TXT contains some text, which needs to be displayed such that every next character is separated by a symbol ‘#’. 8. Write a statement in Python to open a text file STORY.TXT so that new contents can be added at the end of it.
  • 117. PROGRA MS 9. Write a method in Python to read lines from a text file INDIA.TXT, to find and display the occurrence of the word ‘‘India’’. For example : If the content of the file is ‘‘India is the fastest growing economy. India is looking for more investments around the globe. The whole world is looking at India as a great market. Most of the Indians can foresee the heights that India is capable of reaching.’’
  • 118. PROGRA MS 10. Write a function to count total number of spaces, lines and characters in a given line of text
  • 119. PROGRA MS 11. Write a function to count total number of digits in a given line of text
  • 120. PROGRA MS 12. Write a function to copy the content of notes.txt to sub.txt NOTES.txt FILE
  • 121. PROGRA MS 12. Write a function to copy the content of notes.txt to sub.txt
  • 122. PROGRAM - OUTPUT 12. Write a function to copy the content of notes.txt to sub.txt SUB.txt FILE
  • 123. PROGRAM - OUTPUT 13. Write a function to append or add a line of text in notes.txt NOTES.txt FILE
  • 124. PROGRA MS 13. Write a function to append or add a line of text in notes.txt
  • 125. PROGRAM - OUTPUT 13. Write a function to append or add a line of text in notes.txt
  • 126. PROGRA MS 14. Write a function to display total number of lines in a notes.txt file. NOTES.txt FILE
  • 127. PROGRA MS 14. Write a function to display total number of lines in a notes.txt file. NOTES.txt FILE
  • 128. PROGRA MS 14. Write a function to display total number of lines in a notes.txt file.
  • 129. PROGRAM - OUTPUT 14. Write a function to display total number of lines in a notes.txt file. OUTPU T
  • 130. PROGRA MS ANTOHER METHOD 14. Write a function in pythonto countthe total number of lines in a file ‘Mem.txt’
  • 131. PROGRA MS 14. Write a function in pythonto countthe total number of lines in a file ‘Mem.txt’ ‘Mem.txt’ file contains
  • 132. PROGRA MS 14. Write a function in pythonto countthe total number of lines in a file ‘Mem.txt’
  • 133. PROGRA MS 15. Writea function to display last line of notes.txt file. NOTES.txt FILE
  • 134. PROGRA MS 15. Writea function to display last line of notes.txt file.
  • 135. PROGRAM - OUTPUT OUTPU T 15. Writea function to display last line of notes.txt file.
  • 136. PROGRA MS 16. Write a function COUNT_DO( ) in Python to count the presence of a word ‘do’ in a text file “MEMO.TXT”. Example : is a s If the content of the file “MEMO.TXT” follows: I will do it, if you request me to do it. It would have been done much earlier. ) will display the The function COUNT_DO( following message: Count of -do- in flie:
  • 137. PROGRA MS 17. Write a function in Python to count the no. of “Me” or “My” words present in a text file “DIARY.TXT”. If the file “DIARY.TXT” content is as follows : My first book was Me and My family. It gave me chance to be known to the world. The output of the function should be Count of Me/ My in file :
  • 138. PROGRA MS 18. Write a function in Python to count and display the number of lines starting with alphabet ‘A’ present in a text file “LINES.TXT”. Example: If the file “LINES.TXT” contains the following lines, A boy is playing there. There is a playground. An aeroplane is in the sky. Alphabets and numbers are allowed in the password.
  • 139. PROGRA MS 19. Write a function in Python to read the content of a text file “DELHI.TXT” and display all those lines on screen, which are Either starting with ‘D’ or starting with ‘M’. DELHI.TXT File
  • 141. PROGRA MS 20. Write a function in Python to count the number of alphabets present in a text file “NOTES.TXT”. NOTES.TXT FILE
  • 142. PROGRA MS 20. Write a function in Python to count the number of alphabets present in a text file “NOTES.TXT”. NOTES.TXT FILE
  • 145. CBSE QUESTION PAPER 2015 Delhi 4(a) Differentiate between the following : 1 (i) f = open(‘diary.txt’, ‘r’) (ii)f = open(‘diary.txt’, ‘w’) 4(b) Write a method in python to read the content from a text file diary.txt line by line and display the same on screen. 2
  • 147. CBSE QUESTION PAPER 2016 Delhi 4. (a) Write a statement in Python to perform the following operations : 1  To open a text file “BOOK.TXT” in read mode To open a text file “BOOK.TXT” in write mode 4(b) Write a method in python to read the content from a text file diary.txt line by line and display the same on screen. 2
  • 149. CBSE QUESTION PAPER 2017 Delhi 4 (a) Differentiate between file modes r+ and rb+ with respect to Python. 1 4(b) Write a method in Python to read lines from a text file MYNOTES.TXT, and display those lines, which are starting with the alphabet K 2
  • 151. CBSE QUESTION PAPER 2018 AI 4 (a) Write a statement in Python to open a text file STORY.TXT so that new contents can be added at the end of it. 1 4 (b) Write a method in Python to read lines from a text file INDIA.TXT, to find and display the 2 occurrence of the word ‘‘India’’. For example : If the content of the file is ‘‘India is the fastest growing
  • 152. CBSE QUESTION PAPER 2018 AI India is looking for more investments around the globe. The whole world is looking at India as a great market. Most of the Indians can foresee the heights that India is capable of reaching.’’ The output should be 4. 2
  • 154. ADDITIONAL PROGRAMS 1. Write a Python program to read an entire text file. 2. Write a Python program to read first n lines of a file. 3. Write a Python program to append text to a file and display the text. 4. Write a Python program to read last n lines of a file. 5. Write a Python program to read last n lines of a file.
  • 155. 1. Write a Python program to read a file line by line and store it into a list. 2. Write a Python program to read a file line by line store it into a variable. 3. Write a Python program to read a file line by line store it into an array. 4. Write a python program to find the longest words. 5. Write a Python program to count the number of lines in a text file. 6. Write a Python program to count the frequency of words in a file. ADDITIONAL PROGRAMS
  • 156. 5. Write a Python program to read a file line by line and store it into a list. 6. Write a Python program to read a file line by line store it into a variable. 7. Write a Python program to read a file line by line store it into an array. 8. Write a python program to find the longest words. 9. Write a Python program to count the number of lines in a text file. 10.Write a Python program to count the frequency of words in a file. ADDITIONAL PROGRAMS
  • 157. CLASS TEST 1.Write a program to count total no of spaces,words,characters,lines in a msg.txt file. 2.What is file? 3.Differentiate between text files and binary files. 4.Write a program to copy the content of notes.txt from 3rd character to till end of file to para.txt 5. Write a program to create binary file Time: 40 Min Max Marks: 40 Class : XII Topic: FILE HANDLING Each Question carries 4 Marks