[Tutor] split a string inside a list

[Peter Otten]

Kayla Hiltermann wrote:

> i am trying to make a pythagorean triples checker (a^2 + b^2 = c^2). the
> user enters three sides to a triangle and my code determines if it is a
> pythagorean triple (aka right triangle) or not. i have the entire code
> pretty much done, except i want to account for variability in user input,
> like using commas or just spaces. the user input is initially a string,
> but is converted to a list once run through .split() . I would like to
> split the user input by commas or spaces, so: 3 4 5 3,4,5 3, 4, 5 all
> become: [“3", “4", “5"]. yes, the inputs are strings but i convert - or
> make sure - they are integers later in the program. 

Here's the trick: convert the commas to space, then use the string method to 
split:

>>> def my_split(s):
...     return s.replace(",", " ").split()
... 
>>> my_split("1 2 3")
['1', '2', '3']
>>> my_split("1,2,3")
['1', '2', '3']
>>> my_split("1, 2, 3")
['1', '2', '3']
>>> my_split("1, 2, 3,,,")
['1', '2', '3']

When you know it it's easy :)

> my main issue is that
> i cannot split by commas or spaces at the same time. i tried using the
> vertical bar - .split(“ |,”) but it only executed the split by space, not
> the split by comma. 

The str.split() method does not understand regular expressions. You need 
re.split() for this:

>>> import re
>>> re.split(" |,", "1 2 3")
['1', '2', '3']
>>> re.split(" |,", "1,2,3")
['1', '2', '3']
>>> re.split(" |,", "1, 2, 3")
['1', '', '2', '', '3']

To accept a combination of one comma and whitespace:

>>> re.split(r"\s*[,\s]\s*", "1, 2    , 3")
['1', '2', '3']

Or just look for digits:

>>> re.findall(r"\d+", "1, 2    , 3")
['1', '2', '3']

But I recommend that you stick with the str.split() approach shown first.

> as of now, i can only split by either. the issue is
> that when i split by spaces - .split(“ ) , “3,4,5” does not split and
> becomes the list [“3,4,5”]. on the other hand, “3, 4, 5” does split, but
> becomes [“3,”, “4,”, “5”]. the problem is the same if i replace the
> .split(“ “) by split(“,”), only the commas are replaced by spaces.