File Handling in Python

• A file is a collection of data stored on a secondary storage device like hard

disk.
• File path: Files that we use are stored on a storage medium like hard disk.
You have to give the file path to open that file.

There are two types of paths:

• Relative path: is specified relative to the program’s current working
directory. For example: file1.txt
• Absolute Path: always contain root and the complete directory list to
specify the exact location of the file. For example:
C:\student\documents\file1.txt

Types of files:
• Like C, Python also supports two types of files: text files and binary files.
• Contents of a binary file are not human readable. If you want that data stored in the file
must be human readable then store the data in a text file.
• In a text file, each line of data ends with a newline character i.e \n. Each file ends with
a special character called the end-of-file (EOF) marker. Each line in a text file can have
maximum of 255 characters.
••
•
Python File Handling
➢ Python too supports file handling and allows users to handle files i.e., to
read and write files, along with many other file handling options, to
operate on files.

➢ Python treats files differently as text or binary and this is important. Each
line of code includes a sequence of characters and they form a text file.
Each line of a file is terminated with a special character, called the EOL or
End of Line characters like comma {,} or newline character. It ends the
current line and tells the interpreter a new one has begun.

Advantages of File Handling

• Versatility: File handling in Python allows you to perform a wide
range of operations, such as creating, reading, writing, appending,
renaming, and deleting files.
• Flexibility: File handling in Python is highly flexible, as it allows
you to work with different file types (e.g. text files, binary files,
CSV files, etc.), and to perform different operations on files (e.g.
read, write, append, etc.).
 • User–friendly: Python provides a user-friendly interface for file
handling, making it easy to create, read, and manipulate files.
• Cross-platform: Python file-handling functions work across
different platforms (e.g. Windows, Mac, Linux), allowing for
seamless integration and compatibility.

Disadvantages of File Handling

• Error-prone: File handling operations in Python can be prone to
errors, especially if the code is not carefully written or if there are
issues with the file system (e.g. file permissions, file locks, etc.).
• Security risks: File handling in Python can also pose security risks,
especially if the program accepts user input that can be used to
access or modify sensitive files on the system.
• Complexity: File handling in Python can be complex, especially
when working with more advanced file formats or operations.
Careful attention must be paid to the code to ensure that files are
handled properly and securely.
• Performance: File handling operations in Python can be slower
than other programming languages, especially when dealing with
large files or performing complex operations.

The open() Function

This function creates a file object, which would be utilized to call
other support methods associated with it.

Syntax

file object = open(file_name [, access_mode][, buffering])

Here are the parameter details −

• file_name − The file_name argument is a string value that

contains the name of the file that you want to access.
• access_mode − The access_mode determines the mode in
which the file has to be opened, i.e., read, write, append,
etc. A complete list of possible values is given below in the
table. This is an optional parameter and the default file
access mode is read (r).
 • buffering − If the buffering value is set to 0, no buffering
takes place. If the buffering value is 1, line buffering is
performed while accessing a file. If you specify the buffering
value as an integer greater than 1, then buffering action is
performed with the indicated buffer size. If negative, the
buffer size is the system default (default behavior).

File Opening Modes

Following are the file opening modes –

Sr.No. Modes & Description

r
1 Opens a file for reading only. The file pointer is placed at
the beginning of the file. This is the default mode.
rb

2 Opens a file for reading only in binary format. The file

pointer is placed at the beginning of the file. This is the
default mode.
r+
3 Opens a file for both reading and writing. The file pointer
placed at the beginning of the file.
rb+

4 Opens a file for both reading and writing in binary

format. The file pointer placed at the beginning of the
file. C
w

5 Opens a file for writing only. Overwrites the file if the file
exists. If the file does not exist, creates a new file for
writing.
b
6
Opens the file in binary mode
t
7
Opens the file in text mode (default)
+
8
open file for updating (reading and writing)
 wb
Opens a file for writing only in binary format. Overwrites
9
the file if the file exists. If the file does not exist, creates
a new file for writing.
w+
Opens a file for both writing and reading. Overwrites the
10
existing file if the file exists. If the file does not exist,
creates a new file for reading and writing.
wb+
Opens a file for both writing and reading in binary
11 format. Overwrites the existing file if the file exists. If the
file does not exist, creates a new file for reading and
writing.
a
Opens a file for appending. The file pointer is at the end
12 of the file if the file exists. That is, the file is in the
append mode. If the file does not exist, it creates a new
file for writing.
ab
Opens a file for appending in binary format. The file
pointer is at the end of the file if the file exists. That is,
13 the file is in the append mode. If the file does not exist,
it creates a new file for writing.

a+
Opens a file for both appending and reading. The file
14 pointer is at the end of the file if the file exists. The file
opens in the append mode. If the file does not exist, it
creates a new file for reading and writing.
ab+
Opens a file for both appending and reading in binary
15 format. The file pointer is at the end of the file if the file
exists. The file opens in the append mode. If the file does
not exist, it creates a new file for reading and writing.
x
16 open for exclusive creation, failing if the file already
exists
 Explain different file object attribute with example.

Exapmle:

The close() method

Once all the operations are done on the file, we must close it through our Python script
using the close() method. Any unwritten information gets destroyed once
the close() method is called on a file object.
Python automatically closes a file when the reference object of a file is reassigned to
another file. It is good practice to close the file once all the operations are done.

The syntax to use the close() method is given below.

Syntax

1. fileobject.close()

Consider the following example.

1. # opens the file file.txt in read mode

2. fileptr = open("file.txt","r")
3. if fileptr:
4. print("file is opened successfully")
5. #closes the opened file
6. fileptr.close()

After closing the file, we cannot perform any operation in the file. The file needs to be
properly closed. If any exception occurs while performing some operations in the file
then the program terminates without closing the file.

We should use the following method to overcome such type of problem.

1. try:
2. fileptr = open("file.txt")
3. # perform file operations
4. finally:
5. fileptr.close()

NOTE: Once the file is closed using the close() method, any attempt to
use the file object will result in an error.

The with statement

The with statement is useful in the case of manipulating the files. It is used in the
scenario where a pair of statements is to be executed with a block of code in between.

The syntax to open a file using with the statement is given below.

1. with open(<file name>, <access mode>) as <file-pointer>:

 2. #statement suite

The advantage of using with statement is that it provides the guarantee to close the
file regardless of how the nested block exits.

It is always suggestible to use the with statement in the case of files because, if the
break, return, or exception occurs in the nested block of code then it automatically
closes the file, we don't need to write the close() function. It doesn't let the file to
corrupt.

Consider the following example.

Example

1. with open("file.txt",'r') as f:
2. content = f.read();
3. print(content)

The read() method

To read a file using the Python script, the Python provides the read() method.
The read() method reads a string from the file. It can read the data in the text as well
as a binary format.

The syntax of the read() method is given below.

Syntax:

1. fileobj.read(<count>)

Here, the count is the number of bytes to be read from the file starting from the
beginning of the file. If the count is not specified, then it may read the content of the
file until the end.

Consider the following example.

Example

1. #open the file.txt in read mode. causes error if no such file exists.
2. fileptr = open("file2.txt","r")
3. #stores all the data of the file into the variable content
4. content = fileptr.read(10)
 5. # prints the type of the data stored in the file
6. print(type(content))
7. #prints the content of the file
8. print(content)
9. #closes the opened file
10. fileptr.close()

Output:

<class 'str'>
Python is

In the above code, we have read the content of file2.txt by using the read() function.
We have passed count value as ten which means it will read the first ten characters
from the file.

If we use the following line, then it will print all content of the file.

1. content = fileptr.read()
2. print(content)

Output:

Python is the modern-day language. It makes things so simple.

It is the fastest-growing programing language Python has easy an syntax and
user-friendly interaction.

Read file through for loop

We can read the file using for loop. Consider the following example.

1. #open the file.txt in read mode. causes an error if no such file exists.
2. fileptr = open("file2.txt","r");
3. #running a for loop
4. for i in fileptr:
5. print(i) # i contains each line of the file

Output:

Python is the modern day language.

It makes things so simple.

Python has easy syntax and user-friendly interaction.

Read Lines of the file
Python facilitates to read the file line by line by using a function readline() method.
The readline() method reads the lines of the file from the beginning, i.e., if we use the
readline() method two times, then we can get the first two lines of the file.

Consider the following example which contains a function readline() that reads the
first line of our file "file2.txt" containing three lines. Consider the following example.

Example 1: Reading lines using readline() function

1. #open the file.txt in read mode. causes error if no such file exists.
2. fileptr = open("file2.txt","r");
3. #stores all the data of the file into the variable content
4. content = fileptr.readline()
5. content1 = fileptr.readline()
6. #prints the content of the file
7. print(content)
8. print(content1)
9. #closes the opened file
10. fileptr.close()

Output:

Python is the modern day language.

It makes things so simple.

We called the readline() function two times that's why it read two lines from the file.

Python provides also the readlines() method which is used for the reading lines. It
returns the list of the lines till the end of file(EOF) is reached.

Example 2: Reading Lines Using readlines() function

1. #open the file.txt in read mode. causes error if no such file exists.
2. fileptr = open("file2.txt","r");
3.
4. #stores all the data of the file into the variable content
5. content = fileptr.readlines()
6.
 7. #prints the content of the file
8. print(content)
9.
10. #closes the opened file
11. fileptr.close()

Output:

['Python is the modern day language.\n', 'It makes things so simple.\n',

'Python has easy syntax and user-friendly interaction.']

writelines() method:

It is used to write a list of strings. Whereas write() method does not accept list,
number type argument only string type argument is accepted.
Example:
f1=open("file3.txt","w")
lines=["hello world","welcome to programmming","enjoy
learning"]
f1.writelines(lines)
f1=open("file3.txt","r")
print(f1.read())
Output:
hello worldwelcome to programmmingenjoy learning

append() method

Once you have stored some data in a file, you can always open file again to write
more data. For appending a data, mode is used “a”. while write() overwrites
existing data to write the new data in the file.
Example:
f=open("deepika.txt","a")
f.write("\nmy name is deepika")
f.close()
f=open("deepika.txt","r")
print(f.read())

Output:

i live in meerut
my name is Deepika

File Pointer positions

Python provides the tell() method which is used to print the byte number at which the
file pointer currently exists. Consider the following example.

1. # open the file file2.txt in read mode

2. fileptr = open("file2.txt","r")
3.
4. #initially the filepointer is at 0
5. print("The filepointer is at byte :",fileptr.tell())
6.
7. #reading the content of the file
8. content = fileptr.read();
 9.
10. #after the read operation file pointer modifies. tell() returns the location of the
fileptr.
11.
12. print("After reading, the filepointer is at:",fileptr.tell())

Output:

The filepointer is at byte : 0

After reading, the filepointer is at: 117

Modifying file pointer position

In real-world applications, sometimes we need to change the file pointer location
externally since we may need to read or write the content at various locations.

For this purpose, the Python provides us the seek() method which enables us to modify
the file pointer position externally.

The syntax to use the seek() method is given below.

Syntax:

1. <file-ptr>.seek(offset[, from)

The seek() method accepts two parameters:

offset: It refers to the new position of the file pointer within the file.

from: It indicates the reference position from where the bytes are to be moved. If it is
set to 0, the beginning of the file is used as the reference position. If it is set to 1, the
current position of the file pointer is used as the reference position. If it is set to 2, the
end of the file pointer is used as the reference position.

Consider the following example.

Example 1

1. # open the file file2.txt in read mode

2. fileptr = open("file2.txt","r")
3.
4. #initially the filepointer is at 0
5. print("The filepointer is at byte :",fileptr.tell())
 6.
7. #changing the file pointer location to 10.
8. fileptr.seek(10);
9.
10. #tell() returns the location of the fileptr.
11. print("After reading, the filepointer is at:",fileptr.tell())

Output:

The filepointer is at byte : 0

After reading, the filepointer is at: 10

Example 2

Python OS module
Renaming the file
The Python os module enables interaction with the operating system. The os module
provides the functions that are involved in file processing operations like renaming,
deleting, etc. It provides us the rename() method to rename the specified file to a new
name. The syntax to use the rename() method is given below.

Syntax:

1. rename(current-name, new-name)

The first argument is the current file name and the second argument is the modified
name. We can change the file name by passing these two arguments.

Example 1:

1. import os
2.
3. #rename file2.txt to file3.txt
4. os.rename("file2.txt","file3.txt")

Output:

The above code renamed current file2.txt to file3.txt

Removing the file

The os module provides the remove() method which is used to remove the specified
file. The syntax to use the remove() method is given below.

1. remove(file-name)

Example 1

1. import os;
2. #deleting the file named file3.txt
3. os.remove("file3.txt")

1. Program to demonstrate the use of seek(), tell() and readline().

Example:
fob=open("texting.txt","w")
fob.write("This is the first line \n This is the second line")
fob=open("texting.txt")
line=fob.readline()
print("read line %s" %(line))
#To get the current position of the file
position=fob.tell()
print("Current position %d" %(position))
print("\n")
#Repositioning pointer at the begining once again
position1=fob.seek(0)
ran=fob.read(10)
print("Repositioning the file pointer to the begining of the file",ran)
print("\n")
#copying contents of one file to another.
with open("texting.txt")as fa:
with open("out1.txt","w")as fa1:
for line in fa:
fa1.write(line)
print("contents are copied successfully")

2.Program to write numbers from 1 to 20 to the output file “t.txt”

f=open("t.txt","w")
for i in range(1,21):
x=str(i)+" "
f.write(x)
f.close()
f=open("t.txt","r")
print(f.read())
Output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

3. Program to read the contents of a file.

Ans:

4. Program to check End of file is reached.

f=open("deepika.txt","r")
eof=f.read()
if(eof==""):
print("END OF FILE")
Output:
END OF FILE

5. Program to demonstrate the use of r+ mode

f=open("file1.txt","w")
f.write("python programming language\n")
f.write("object oriented language\n")
f.write("c programming language")
f.close()
f=open("file1.txt","r+")
f.write("\ni work in meerut")
print(f.read())
Output:
python programming language
object oriented language
c programming language
i work in meerut

6. Program to use the split() method in the file

f=open("deepika.txt","r+")
b=f.read()
print(b)
c=b.split("\n")
print(c)
for i in c:
print(i)
Output:
i live in meerut
my name is deepika
my name is deepika
['i live in meerut', ' my name is deepika', 'my name is deepika']
i live in meerut
my name is deepika
my name is deepika

7. Program that accepts filename as an input from the user. Open the file and count the
number of times a character appears in the file.

filename=input("enter file name ")

with open(filename) as f:
text=f.read()
letter=input("enter letter to be searched ")
count=0
for i in text:
if i==letter:
count=count+1
print(letter,"appears",count,"times in file")
Output:
enter file name file13.txt
enter letter to be searched a
a appeaars 8 times in file

8. Program that copies contents of one file into another file in such a way that all
comments lines are skipped and not copied to second file.

with open("first.txt","w") as f:
f.write("# this is the first file\n")
f.write("i am deepika gupta\n")
f.write("i am a teacher")

with open("first.txt","r") as f:
with open("second.txt","w") as f1:
while True:
a=f.readline()
if len(a)!=0:
 if a[0]=='#':
continue
else:
f1.write(a)
else:
break

or using another open() method

f1=open("first.txt","r")
f2=open("second.txt","w")
while True:
a=f1.readline()
if len(a)!=0:
if a[0]=='#':
continue
else:
f2.write(a)
else:
break

f=open("second.txt","r")
print(f.read())

Output:
i am deepika gupta
i am a teacher

9. Program that reads a file line by line. Each line read from the file is copied to another
file with line numbers specified at the beginning of the line.
f1=open("one.txt","r")
f2=open("second.txt","w")
num=1
for i in f1:
print(i)
f2.write(str(num)+":"+i)
num=num+1
f1.close()
f2.close()

Output:
1:Mango
2:banana
3:Grapes
10. Program to count the number of words in a text file.

Ans:

12. Program to read a string from the user and appends it into a file.

Ans:
13. Program to count the occurrences of a word in a text file

Ans:

14. Python Program to copy the contents of one file into another.

Ans: