CODEWITHSUNDEEP
pythonpython-2.7os.path
ATOzTOA
ATOzTOA

Reputation: 35980

Python os.path.join() on a list

I can do

>>> os.path.join("c:/","home","foo","bar","some.txt")
'c:/home\\foo\\bar\\some.txt'

But, when I do

>>> s = "c:/,home,foo,bar,some.txt".split(",")
>>> os.path.join(s)
['c:/', 'home', 'foo', 'bar', 'some.txt']

What am I missing here?

Upvotes: 148

Views: 207579

Answers (5)

ATOzTOA
ATOzTOA

Reputation: 35980

The problem is, os.path.join doesn't take a list as argument, it has to be separate arguments.

To unpack the list into separate arguments required by join (and for the record: list was obtained from a string using split), use * - or the 'splat' operator, thus:

>>> s = "c:/,home,foo,bar,some.txt".split(",")
>>> os.path.join(*s)
'c:/home\\foo\\bar\\some.txt'

Upvotes: 263

Thorsten Kranz
Thorsten Kranz

Reputation: 12765

Assuming join wasn't designed that way (which it is, as ATOzTOA pointed out), and it only took two parameters, you could still use the built-in reduce:

>>> reduce(os.path.join,["c:/","home","foo","bar","some.txt"])
'c:/home\\foo\\bar\\some.txt'

Same output like:

>>> os.path.join(*["c:/","home","foo","bar","some.txt"])
'c:/home\\foo\\bar\\some.txt'

Just for completeness and educational reasons (and for other situations where * doesn't work).

Hint for Python 3

reduce was moved to the functools module.

Upvotes: 34

Greg
Greg

Reputation: 5588

It's just the method. You're not missing anything. The official documentation shows that you can use list unpacking to supply several paths:

s = "c:/,home,foo,bar,some.txt".split(",")
os.path.join(*s)

Note the *s intead of just s in os.path.join(*s). Using the asterisk will trigger the unpacking of the list, which means that each list argument will be supplied to the function as a separate argument.

Upvotes: 12

Nishant
Nishant

Reputation: 21914

This can be also thought of as a simple map reduce operation if you would like to think of it from a functional programming perspective.

import os
folders = [("home",".vim"),("home","zathura")]
[reduce(lambda x,y: os.path.join(x,y), each, "") for each in folders]

reduce is builtin in Python 2.x. In Python 3.x it has been moved to itertools However the accepted the answer is better.

This has been answered below but answering if you have a list of items that needs to be joined.

Upvotes: 2

Sebastian Mach
Sebastian Mach

Reputation: 39109

I stumbled over the situation where the list might be empty. In that case:

os.path.join('', *the_list_with_path_components)

Note the first argument, which will not alter the result.

Upvotes: 18

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