doing "nothing" in else command of if-else clause

Question

Code:

for i in range(1000):
    print(i) if i%10==0 else pass

Error:

File "<ipython-input-117-6f18883a9539>", line 2
    print(i) if i%10==0 else pass
                            ^
SyntaxError: invalid syntax

Why isn't 'pass' working here?

Are you asking "how do I make this work" or "I'm curious why this [unusual] syntax isn't permissible"? — hoyland, Apr 25 '18 at 10:15
this is a small example, i need to extend this on a different problem — Mysterious, Apr 25 '18 at 10:15
Dupes: https://stackoverflow.com/questions/394809/does-python-have-a-ternary-conditional-operator and https://stackoverflow.com/questions/14474168/using-statements-on-either-side-of-a-python-ternary-conditional and https://stackoverflow.com/questions/7818992/python-ternary-operator-with-assignment — Aran-Fey, Apr 25 '18 at 10:16
I found [yet another variation](https://stackoverflow.com/questions/32954481/why-is-this-simple-conditional-expression-not-working) of the same issue, if you prefer that one. — Aran-Fey, Apr 25 '18 at 10:28
@Aran-Fey please save yourself the effort and time to find duplicate answers and read the expected correct answer below by BcK — Mysterious, Apr 25 '18 at 10:33
Personally in this situation I would use continue as it seems appropriate to use seeing as it’s a for loop. — Thomas Upson, Apr 25 '18 at 10:36
@ThomasUpson if you put "continue" instead of 'pass', it will still give syntax error. Try it. — Mysterious, Apr 25 '18 at 10:38

score 17 · Accepted Answer · answered Apr 25 '18 at 10:20

17

This is not a good way of doing this, if you see this problem the structure of your code might not be good for your desires, but this will helps you:

 print(i) if i%10==0 else None

answered Apr 25 '18 at 10:20

Mehrdad Pedramfar

This definitely makes more sense, but why isn't 'pass' working in this condition? – Mysterious Apr 25 '18 at 10:22
3

It's an expression, not an indented block. @VarenGupta – BcK Apr 25 '18 at 10:24
Oh, I see. That makes sense. Thanks! – Mysterious Apr 25 '18 at 10:25
1

Yes BcK is right. you use pass for presenting a empty indented block, pass it not for do nothing. @VarenGupta – Mehrdad Pedramfar Apr 25 '18 at 10:25

score 2 · Answer 2 · answered Apr 25 '18 at 10:27

This is not a direct answer to your question, but I would like suggest a different approach.

First pick the elements you want to print, then print them. Thus you'll not need empty branching.

your_list = [i for i in range(100) if i%10]
# or filter(lambda e: e%10 == 0, range(100))
for number in your_list:
    print number

2 Answers2