我可以在Python上的if条件中为变量赋值

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?

Answer 1

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

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

Answer 2

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.