Can I assign value to a variable among if condition on Python

Question

I write my code that way, I want to assign matched values to 'm' but lst[1] may not including the pat I want. if it does, so I'll keep do something about 'm' eg: m.group(2).split() ....

  if re.match(pat, lst[1]):
       m=re.match(pat, lst[1])

But I don't want to repeat the re.match(pat, lst[1]) twice.

I want to achieve in that way

  if m = re.match(pat, lst[i])

but it shows me "invalid syntax error. any ideas?

its like asking for using braces instead of indentation in Python — perreal
– perreal, Commented Aug 29, 2013 at 11:10
@ThePhysicist that's exactly what I thought when I read it. As it currently stands, OP is saying he doesn't want to not repeat himself, or equivalently that he does wish to repeat himself. — AJMansfield
– AJMansfield, Commented Aug 29, 2013 at 11:17
Why is this even a problem? If you just do m = re.match(pat, lst[i]) then m will be None if there are no matches; you can completely get rid of the if. — Burhan Khalid
– Burhan Khalid, Commented Aug 29, 2013 at 11:30

ThePhysicist · Accepted Answer · 2013-08-29 11:05:44Z

4

Just assign the value beforehand and check if it's None:

m = re.match(pat,lst[1])
if not m:
  del m

answered Aug 29, 2013 at 11:05

ThePhysicist

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3 Comments

newBike Over a year ago

Thank you~ I forgot your solution

ThePhysicist Over a year ago

You're welcome! Coming from Ruby I'm sometimes tempted to use unless (a = ...) do syntax as well, which sadly (or luckily!?) does not work in Python...

newBike Over a year ago

ha I love Ruby , but not familiar enough

glglgl · Accepted Answer · 2013-08-29 15:03:15Z

0

You can abuse for for your task.

def for_if(expression):
    if expression:
        yield expression

for m in for_if(re.match(pat, lst[1])):
    # work with m

or just

for m in (i for i in (re.match(pat, lst[1]),) if i):
    # do the same

This is not really helpful for readability, but is the only way to combine assignment and test.

answered Aug 29, 2013 at 15:03

glglgl

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