CODEWITHSUNDEEP
python
IvanP
IvanP

Reputation: 9

difference between two Python statements

How are these two Python statements different:

>>> if a==1 and b==2:
        pass
>>> if a==1:
        if b==2:
            pass

Upvotes: 0

Views: 50

Answers (2)

Mureinik
Mureinik

Reputation: 312116

If these two statements are the entire code (e.g., there's no else to match the if), these two statements will have the same effect.

Upvotes: 2

Mark Tolonen
Mark Tolonen

Reputation: 178090

There is no practical difference. Both must evaluate a==1 and b==2 for pass to execute, and both "short-circuit" and do not evaluate b==2 if a==1 is False.

Here's an example of short-circuiting:

>>> a=1
>>> b=2
>>> if a==1 and b==2:
...   print('pass')
...
pass

Here, the first statement is True so the second is evaluated, but c does not exist:

>>> if a==1 and c==2:
...   print('pass')
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'c' is not defined
>>> if a==1:
...   if c==2:
...     print('pass')
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
NameError: name 'c' is not defined

Here, the first statement is false so the invalid variable is not evaluated:

>>> a=2
>>> if a==1 and c==2:
...   print('pass')
...
>>>
>>> if a==1:
...   if c==2:
...     print('pass')
...
>>>

Upvotes: 1

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