Convert a string list to a tuple in Python

Question

I am trying to convert a string such as 'SUP E P I C' to a tuple containing all the non-spaced strings. For example, if the input is 'SUP E P I C', then the program should return ('S', 'U', 'P', 'E', 'P', 'I', 'C') and I am trying the obvious method of looping, and I started as follows:

for ch in john:
    if ch != ' ':
        j1 += ch
    else:
        # stuff

I'm stuck because I can add the first entry of the tuple but after that skipping the space is just escaping me. Any hints would be much appreciated!

The only problem with your code is that j1 += ch won't work if j1 is a tuple and ch is a string. gnibbler's solution is clearer and simpler, and maybe even faster, but your solution is fine, except for this one problem. — abarnert
– abarnert, Commented Nov 19, 2013 at 0:02

John La Rooy · Accepted Answer · 2013-11-18 23:30:17Z

8

tuples are immutable, so building them up one item at a time is very inefficient. You can pass a sequence directly to tuple

>>> tuple('SUP E P I C'.replace(" ",""))
('S', 'U', 'P', 'E', 'P', 'I', 'C')

or use a generator expression (overkill for this example)

>>> tuple(x for x in 'SUP E P I C' if not x.isspace())
('S', 'U', 'P', 'E', 'P', 'I', 'C')

answered Nov 18, 2013 at 23:30

John La Rooy

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4 Comments

Ahaan S. Rungta Over a year ago

Excellent, just what I was looking for; thanks a lot! I'll upvote/accept once my vote lock and accept lock get free. :)

Ahaan S. Rungta Over a year ago

Sorry, one more question - what if we wanted to replace more than one thing? For example, if we wanted to replace the spaces with blanks (like you did) but also new-line characters with blanks, what might we do then?

John La Rooy Over a year ago

@AhaanRungta, the second version will filter any whitespace. You could also use tuple('SUP E P I C'.translate(None, ' \n'))

Ahaan S. Rungta Over a year ago

Great! Thanks a lot. :) Accepted. But I'll have to wait 12 more minutes to upvote.

abarnert · Accepted Answer · 2013-11-19 00:00:33Z

3

The problem with your code is that you're trying to add a string to a tuple; you need to add a tuple to a tuple:

j1 = ()
for ch in john:
    if ch != ' ':
        j1 += (ch,)

With that one little fix, your original code works.

And it's equivalent to the comprehension given in gnibbler's answer:

j1 = tuple(ch for ch in john if ch != ' ')

… or, for that matter, a filtercall:

j1 = tuple(filter(lambda ch: ch != ' ', john))

Except, of course, that if that "other stuff" is anything non-trivial, you won't be able to easily convert it; you'll need to stick with your original explicit loop. And there's nothing wrong with that.

answered Nov 19, 2013 at 0:00

abarnert

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