How to erase the file contents of text file in Python?

In Python:

open('file.txt', 'w').close()

Or alternatively, if you have already an opened file:

f = open('file.txt', 'r+')
f.truncate(0) # need '0' when using r+

Opening a file in "write" mode clears it, you don't specifically have to write to it:

open("filename", "w").close()

(you should close it as the timing of when the file gets closed automatically may be implementation specific)

Not a complete answer more of an extension to ondra's answer

When using truncate() ( my preferred method ) make sure your cursor is at the required position. When a new file is opened for reading - open('FILE_NAME','r') it's cursor is at 0 by default. But if you have parsed the file within your code, make sure to point at the beginning of the file again i.e truncate(0) By default truncate() truncates the contents of a file starting from the current cusror position.

A simple example

As @jamylak suggested, a good alternative that includes the benefits of context managers is:

with open('filename.txt', 'w'):
    pass