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Python Python Collections (Retired) Lists Redux Disemvoweled

Posted by saro lin
saro lin
Courses Plus Student 531 Points

.join() ?

what is the purpose of .join() ?

2 Answers

Gregory Katchmar
Gregory Katchmar
10,912 Points

Creates a string from a list. Given list['a', 'b', 'c'], the command ', '.join(list) will result in the string "a, b, c"

The command will only work on 100% string lists, so if an integer is in play, no go.

Chris Freeman
Chris Freeman
Treehouse Moderator 68,425 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,425 Points

Extending Gregory's answer, the join() is a string method (operates on the associated string). It says "I am a string. Use me as the glue to 'join' a container of string objects into one long string object".

Many ask why isn't join a list method since that is what is usually joined. As Gregory mentioned, if all of the items in the list to be joined are not cast as strings, then an error is raised. So it makes more sense as a str method. Additionally, you can use a variety of containers as the argument to join:

# a tuple
>>> ' '.join( ('a', 'b', 'c'))
'a b c'
# a dict (note a dict as a container in an iteration context yields it's keys as a list)
>>> my_dict = {'key': 1, 'order': 2, 'is': 3, 'not': 4, 'guaranteed': 5}
>>> ' '.join( my_dict)
'not order key is guaranteed'
Haider Ali
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Haider Ali
Python Development Techdegree Graduate 24,728 Points
Haider Ali
.a{fill-rule:evenodd;}techdegree seal-36
Haider Ali
Python Development Techdegree Graduate 24,728 Points

Hi Saro. As Chris said, `join()' is a method which is used on a string. It can be used to join things together into a string such as items in a list. E.g:

', '.join(['1', '2', '3'])
>>> '1, 2, 3'