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How to delete data from file in Python
  • Difficulty Level : Expert
  • Last Updated : 23 Jan, 2020

When we no longer require data, we usually prefer to erase or delete it so that space can be used up by other data that is important to us. 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.

Refer to the below articles to get the idea about file handling in Python.

Here, we will be learning different approaches that are used while deleting data from the file in Python.

Method 1: When the entire data along with the file, it is in, has to be deleted!

os.remove() method in Python is used to remove or delete a file path. This method can not remove or delete a directory. If the specified path is a directory then OSError will be raised by the method. os.rmdir() can be used to remove directory.



Example:

Before execution:

python-delete-file




# code to delete entire data along with file
import os
  
# check if file exists
if os.path.exists("sample.txt"):
    os.remove("sample.txt")
  
    # Print the statement once
    # the file is deleted 
    print("File deleted !"
  
else:
  
    # Print if file is not present 
    print("File doesnot exist !"


python-delete-file

After execution:

python-delete-file

Note: For more information, refer to Python | os.remove() method

Method 2: When the entire data has to be deleted but not the file it is in !



Truncate() method truncate the file’s size. If the optional size argument is present, the file is truncated to (at most) that size. The size defaults to the current position. The current file position is not changed. Note that if a specified size exceeds the file’s current size, the result is platform-dependent: possibilities include that the file may remain unchanged, increase to the specified size as if zero-filled, or increase to the specified size with undefined new content. To truncate the file, you can open the file in append mode or write mode.

Example:

Before execution:

python-delete-file




# code to delete entire data 
# but not the file, it is in
  
  
# open file 
f = open("sample.txt", "r+"
  
# absolute file positioning
f.seek(0
  
# to erase all data 
f.truncate() 


Output:

python-delete-file

After execution:

python-delete-file

Note: For more information, refer to Python File truncate() Method.

Method 3: Delete a particular data from the file

This can be done by following ways:

  1. Open file in read mode, get all the data from the file. Reopen the file again in write mode and write all data back, except the data to be deleted
  2. Rewrite file in a new file except for the data we want to delete. faster)

Let us see the first one.

Example:

Before execution:

python-delete-file




# code to delete a particular
# data from a file
  
# open file in read mode
with open("sample.txt", "r") as f:
      
    # read data line by line 
    data = f.readlines()
      
# open file in write mode
with open("sample.txt", "w") as f:
      
    for line in data :
          
        # condition for data to be deleted
        if line.strip("\n") != "Age : 20"
            f.write(line)


Output:

python-delete-file

After execution:

python-delete-file

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