Testing an index in a for loop - Python

Question

Very simple problem, although I am having quite a tough time solving it.

Take a look at the code and I will explain below:

def printc(some_text):
    split_text = list(some_text)

    for x in split_text:
        if x is '{'
            # this is what i need help with


printc("{CCyan, {RRed, {YYello)

The idea behind this and it is still very early in the code development, but what I am trying to do is create an iterator that searches through "split_text" and finds the character '{' then i want to test what character is situated right next to it. How would i go about doing that?

For example is searches through split_text and finds the first { i want to see if the character next to it is either A, B, C, etc...

Any ideas?

Do you want expected the function to print `C`, `R`, and `Y` if the input is `"{CCyan, {RRed, {YYello"` ? — falsetru, Aug 13 '14 at 13:42
also, you shouldn't be using `is` here. read up on the difference between `==` and `is`, it's important — acushner, Aug 13 '14 at 13:44
@acushner i def will do that, i always thought it was shorthand for the same thing to make it more 'pseudo-code' — pypy, Aug 13 '14 at 13:46
what's the real problem you are trying to solve? also, strings are already a list.. you don't need to create a list out of it. — Corley Brigman, Aug 13 '14 at 13:48
@CorleyBrigman I find it easier to split up a string into individual characters, mess with them as I see fit and splice them back together. May not be the best way, but it works for me so far. — pypy, Aug 13 '14 at 13:49
@pypy, regarding a list of characters, did you know that `for x in some_text` gives the same result as `for x in list(some_text)` minus creating a completely unnecessary list? — acushner, Aug 13 '14 at 17:14

score 4 · Answer 1 · answered Aug 13 '14 at 13:44

4

Much easier with a single regex.

import re
re.findall('{(.)', some_text)

outputs:

['C', 'R', 'Y']

answered Aug 13 '14 at 13:44

Daniel Roseman

588,541
66
880
895

score 2 · Answer 2 · answered Aug 13 '14 at 13:43

2

for x, y in zip(some_text, some_text[1:]):
    if x == '{':
        print y

you could even make it simpler:

chars = [y for (x, y) in zip(some_text, some_text[1:]) if x == '{']

answered Aug 13 '14 at 13:43

acushner

9,595
1
34
34

score 1 · Answer 3 · answered Aug 13 '14 at 13:43

I usually iterate in pairs if I need something like this:

from itertools import tee, izip

def pairwise(iterable):
    """Iterate in pairs

    >>> list(pairwise([0, 1, 2, 3]))
    [(0, 1), (1, 2), (2, 3)]
    >>> tuple(pairwise([])) == tuple(pairwise('x')) == ()
    True
    """
    a, b = tee(iterable)
    next(b, None)
    return izip(a, b)

Usage is like:

for left, right in pairwise(iterable):
    ...

Testing an index in a for loop - Python

3 Answers3