How to cut and limit a string size at the same time?

Question

Here is an example of what i need.

Suppose that we have the following string:

str = "/home/user/folder/MyVeryLongFileName.foo"

I have multiple operations to do on this one :

1. remove the path (assuming i have its length) :

   str = str[path_length:]
   

2. revome the extension (always 4 char in my case) :

   str = str[path_length:-4]
   

   So, right now my string looks like MyVeryLongFileName

3. Now I would like to limit its size at 15 characters. Is it possible to do it in the same expression ? Or may I have to do it after the 2 previous operations ?

Answer 1

If you want only the first 15 characters, then you can slice the string again, like this:

file_name[path_length:-4][:15]

If you really are dealing with filenames, you might want to go with

>>> file_name = "/home/user/folder/MyVeryLongFileName.foo"
>>> import os
>>> print os.path.split(file_name)[1].rpartition(".")[0][:15]
MyVeryLongFileN

Or:

>>> print os.path.basename(file_name).rpartition(".")[0][:15]
'MyVeryLongFileN'

Also, it would be better to use splitext to get the extension, like this

>>> from os.path import basename, splitext
>>> print splitext(basename(file_name))[0][:15]
MyVeryLongFileN

Answer 2

You can get the filename with this:

>>> print str.split('/')[-1]
MyVeryLongFileName.foo

Remove the extension with:

>>> print str.split('.')[0]
/home/user/folder/MyVeryLongFileName

Limit the file name to 15 characters:

>>> print str.split('/')[-1][:15]
MyVeryLongFileN

---

This being said, you can always use the bash utils to extract this info. basename is the tool to get the file and dirname to get the path. See Extract filename and extension in bash for more info.

Answer 3

I would do this:

>>> from os.path import splitext, basename
>>> apath = "/home/user/folder/MyVeryLongFileName.foo"
>>> splitext(basename(apath))[0][:15]
'MyVeryLongFileN'

splitext separates the file-extension from the rest, and we do this on the result of basename which splits the part into the base file-name and the rest of the path. Then we can cut down the remaining string. I would definitely use these methods because they are much more reliable.