CODEWITHSUNDEEP
pythonpython-3.xif-statement
Nurmister
Nurmister

Reputation: 13

Python's Evaluation of If-Else Conditional Statements

I recently encountered an example of an if-else conditional statement and could not understand the rationale behind its output. The following are the statements:

if 0:
    1
else:
    2

Output: 2

I tried different integers in 0's place, and received 1 each time. Is this because the zero in the if condition represents False? But then why do integers other than 1 still satisfy the if condition?

Thanks!

Edit: Thank you for all your answers. I now understand that any integer except 0 in the 'if' statement will make the statement True by default, resulting in an output of 1, in this case.

Upvotes: 1

Views: 429

Answers (3)

Larry Lustig
Larry Lustig

Reputation: 51008

Python will always attempt to determine the "truthiness" of a given value used in a boolean context. In Python any numerical value of 0 (or 0.0) is considered false, and string, dictionary, list, or other iterable (or other class that can report its length) is false if it's empty or has length of 0. Also, None and boolean False are considered false.

Other values are considered true.

More details: https://docs.python.org/2.4/lib/truth.html.

Upvotes: 2

Taufiq Rahman
Taufiq Rahman

Reputation: 5714

1 is considered True while 0 is False,just like in binary.

Any non-zero numeric value is evaluated as True in a conditional statement.

bool  type is just a subtype of int in Python, with 1 == True and 0 == False.

Upvotes: 0

user5179469
user5179469

Reputation:

In Python, bool is a subtype of int. False has the value 0, while other non-zero integers have the subtype bool with the value True.

To see this for yourself try this: False == 0

And to see the subtypes of int try this: int.__subclasses__()

Upvotes: 0

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