Think in python, Chapter 8(lists)

Question

As an exercise, describe the relationship

between string.join(string.split(song)) and song.

(they both refer to a string)

Are they the same for all strings? When would they be different?

I am a little ashamed to ask such a question for a likely simple question but,

I don't get it, what is/are the exception(s)? when are they are different?

Answer 1

split actually splits on one or more occurrences of the delimiter. So " a b c ".split() and "a b c".split() both result in the same list i.e. ['a','b','c']. join only adds a single instance of the delimiter in between consecutive elements of the list. " ".join(['a','b','c'])gives us"a b c"`, which matches out second string but not the first string.

>>> original="     a        b           c    "
>>> " ".join(original.split())
'a b c'

BTW, using string.split and string.join is deprecated. Simply call them as methods of the string you are working on (as in my examples).

Answer 2

By default the split method groups consecutive delimiters together, so if you have them in your original string they'll be lost:

>>> import string
>>> song = "I     am      the      Walrus"
>>> string.join(string.split(song))
'I am the Walrus'

However, if you specify delimiters to split on then consecutive delimiters are not grouped so you can keep the strings the same:

>>> string.join(string.split(song,' '))
'I   am    the    Walrus'