File Handling in Python

File Handling in Python
Prof. Anand A Bhosle
Department of Information technology
International Institute of Information Technology, I²IT
www.isquareit.edu.in

File
• A file is collection of information/data in a
particular format.
• A file has different extension based on data it
stored in it and format it uses for representing
that data.
• A file is typically stored on a Storage medium
such as Disk(hard Disk).
• A file is stored on a disk at a location(path).
International Institute of Information
Technology, I²IT, P-14, Rajiv Gandhi
Infotech Park, Hinjawadi Phase 1, Pune -
411 057
Phone - +91 20 22933441/2/3 | Website -

File Structure
• Files are Stored in a hierarchical structure like
a tree.
• At top of tree there is a root node.
• A root node branches into multiple partitions
or drives.
• Drives are having folders or directories and
files .
• Directories in turn may have another folders
or files
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Files
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C:/Myfile
(Directory)
My Computer
C:(Drive)
A.txt
(Text File)
D:( Drive) E: (Drive)

File Path
• Files can be retrieved or accessed by
traversing through the hierarchical( tree)
structure as shown in above figure.
• So to access a file, we need to traverse from
root node to the node of a file.
• While traversing , we are visiting the nodes in
a sequence to file node is nothing but path or
location of a file.
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File Path
• In figure shown above three drive are root
nodes.
• A text file is stored on D drive , so we start
traversal from D node.
• To access a a.txt file , we will traverse from
node D to node a.txt .
• So the path of the a.txt is :
D:Myfilea.txt
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File Path
“D:Myfilea.txt “ character after dot
indicates the extension of the file.
File can have different extension, example .txt,
.pdf , .docx , . pptx.
In above path character() used to separate
the folders or nodes is known as delimiter.
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Absolute Path
Absolute path is also called complete or full
path.
Absolute path contains path from root node
and all directories and subdirectories that
contains a file
 D:Myfilea.txt path is the example of
absolute path as it contains all nodes from
root node to the a.txt node.
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Relative Path
• A relative path starts with respect to present
working directory.
• A file can be accessed by using absolute path.
• A relative path is combined with another path
to form a complete path.
Example : C:StudentsMyFolderMyfile.txt
If C:Students is present working directory.
Then MyFoldeMyfile.txt is Relative Path
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Types of Files
Python Supports two types of files.
ASCII Text Files
Binary Files.
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ASCII Text Files
In a Text file each character represents a byte.
Each character has an ASCII value associated
with it.
Text files are processed sequentially in
forward direction.
So , text files can perform one operation at a
time(read/write).
Text files can read or write one character at a
time. International Institute of Information
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ASCII Text Files
A text file can contain zero or more characters.
A line in a file can have max 255 characters.
A line end with new line character.
New line character is converted to carriage
return.
A file end with special character called End of
file (EOF).
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ASCII Text Files
• There are two representation of data in text
file.
Internal: integer value will be represented as
number that occupies 2 or 4 bytes of memory
internally.
External : integer value will be represented as
Decimal or hexadecimal string of characters.
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Binary Files
A binary file contain any type of data , but in a
binary form for storing and processing
purpose.
 a binary file is sequence of bytes.
It is also referred to as character stream.
They are not in human readable form.
All executableprogram are stored in binary
file.
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Differences
Binary files requires less space than text files.
Text files are human readable whereas binary
file are not human readable.
Text files are less prone to get corrupted as
compare to binary files.
 Example Text Files : a.txt , a.pdf.
Example Binary file : .png , .jpg
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Opening and Closing Files
• Python has built-in functions to manipulate
files.
The open() Function : to perform any
operation on a file ,file must be opened.
The open() function is used to open a file in
python.
 open() function creates an object , which can
be used to perform different operations on a
file. International Institute of Information
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Syntax of open() function
file_obj = open(‘file_name’,mode)
file_obj : Object returned by open() function ,
which is used to perform different operations
on a file. works as a file handle.
file_name : the name of the file that you want
to open.
mode : indicates the mode in which file is to
be opened.example :read, write, append.
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Access Modes
Access mode is a optional parameter in open
function.
Default access mode in a open function is read
mode.
A file can be accessed in a read or write mode,
but there are multiple combination of these
modes are avaialble.
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Access Modes
Access
Modes
Meaning File pointer
r Default mode ,opens a file in read only mode . at beginning of file.
rb Opens file read only binary format . at beginning of file.
r+ Both reading and writing at beginning of file.
rb + Reading and writing in in binary format at beginning of file.
w
Write only. If file does not exist, new file created. If file
exist ,contents are over written.
at beginning of file.
wb
Opens file in binary format for writing only. If file does
not exist, new file created. If file exist ,contents are
over written.
w+
Opens file for both reading and writing. If file does not
exist, new file created. If file exist ,contents are over
written.
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Basic Operations on Lists
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Access
Modes
Meaning File pointer
wb+
Opens file in binary format for both reading and
writing. If file does not exist, new file created. If file
exist ,contents are over written.
a
Opens a file for appending, if file does not exist it
creates a file.
at the end of file.
ab
Opens a file in binary format for appending, if file
does not exist it creates a file.
at the end of file.
a+
Opens a file for reading and appending , if file does
not exist it creates a file.
at the end of file.
ab+
Opens a file in binary format for reading and
appending , if file does not exist it creates a file.
at the end of file.

File Object
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open() function returns a file object , file object
is used to perform operations on file, which is
also known as file handle.
File handle is different from file , but it used to
access file and perform operations on it.
Even you can print file object
Example : f = open(‘a.txt’,’r’)
Output:< open file ‘a.txt’, mode ‘r’at 0x02A64574>

The File Object Attributes
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File object can be used to access information
about files.
The information about file can be obtained using
different attributes of a file object.
fileobj.closed :returns true if file is closed ,false
otherwise.
fileobj.mode : returns mode in which file is
opened.
fileobj.name : returns the name of the file.

The Close() Method.
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The close() method is used to close the file.
Once file object is closed you can not access a
file.
Python automatically closes a file once file
object is reassigned to different file.
close() method closes a file and releases
resources associated with a file.

Example
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file = open(‘a.txt’,’r’)
file.close()
print(file.name)
print(file.mode)
print(file.closed)
Output :
a.txt
r
True

Reading and Writing Files
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f= open('a.txt','w')
s= input('Enter a text to write to a file')
f.write(s)
print('the Contents Written to a file a.txt are')
f.close()
f=open('a.txt','r')
print(f.read())
f.close()

Reading and writing files
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Output:
Enter a text to write to a file:
Welcome to Python
the Contents Written to a file a.txt are
Welcome to Python

References
International Institute of Information Technology, I²IT, P-14,
Rajiv Gandhi Infotech Park, Hinjawadi Phase 1, Pune - 411
057
Phone - +91 20 22933441/2/3 | Website -
www.isquareit.edu.in | Email - info@isquareit.edu.in
 “Python Programming using Problem Solving
Approach” By Reema Thareja ,Oxford University
Pres.

Thank-You
International Institute of Information Technology, I²IT,
P-14, Rajiv Gandhi Infotech Park, Hinjawadi Phase 1,
Pune - 411 057
Phone - +91 20 22933441/2/3 | Website -
www.isquareit.edu.in | Email - info@isquareit.edu.in
International Institute of Information Technology,
I²IT,
P-14, Rajiv Gandhi Infotech Park, Hinjawadi Phase
1, Pune - 411 057.
Phone - +91 20 22933441/2/3
Website - www.isquareit.edu.in
Email - info@isquareit.edu.in

File Handling in Python

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