How can I replace (or strip) an extension from a filename in Python?

Easy peasy: Simple usage of os.path.splitext()

Dealing with multiple appendages... I mean, extensions

Some files have a lot of .this.that stuff going on—like a potluck party, but for file extensions. How do you handle these? os.path.splitext is your friend.

import os
filename = "archive.tar.gz"
while '.' in filename:  # Yep, we're going round and round!
    filename = os.path.splitext(filename)[0]
# Now everyone left, and 'archive' is alone.
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Ever used SCons? Here's some sugar for you

For the SCons-loving builders among us, os.path.splitext slides in smoothly.

import os
env = Environment()
filename = 'source.c'

# Ssssst.. Password please?
name_without_ext = os.path.splitext(filename)[0]

# Man of steel? No. Man of Source!
object_file = env.Object(target=name_without_ext, source=filename)
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Marching with the times: Enter pathlib

pathlib is the new kid on the block—a Python 3.4+ friendly OO-style way to manipulate file paths.

Nothing to see here... Removing extensions with pathlib

from pathlib import Path
name_without_ext = Path('example.txt').with_suffix('')  # With a flick of the wand
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Spicing things up with a new .extension

from pathlib import Path
new_name = Path('example.txt').with_suffix('.new_extension')  # The shape-shifting spell
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Playing god with our own function

from pathlib import Path

# Yeah, it's a DIY thing.
def replace_ext(filename, new_extension=''):
    # Behind the veil goes the file, and out comes the new one!
    return Path(filename).with_suffix(new_extension)

new_name = replace_ext('example.txt', '.bak')  # A sprinkle of '.bak'
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This function is like a bouncer at a club—it only lets the last extension go.

Roadblocks and how to navigate them

Dealing with the extension-less wanderers

import os
filename = "README"  #Such a lonely file... 
name, extension = os.path.splitext(filename)
# name is 'README', extension is... wait what?
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When filenames have identity crises

Our file 'my.file.name.txt' is not sure if it's a period, a dot, a point, or a .

filename = 'my.file.name.txt'
name_without_ext = filename.rsplit('.', 1)[0]  
# 'my.file.name' - Split personality handled!
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This only removes the last occurrence and lets the others live happily in Dotland.

Assertions: Your friendly neighborhood fact-checker

assert replace_ext('example.txt', '.bak') == 'example.bak'
assert replace_ext('archive.tar.gz', '.bz2') == 'archive.tar.bz2'
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Assertions are like your memory capsules. They remember original cases and help your function avoid an identity crisis.