Function not called when argument expression is buggy

[choucroute1958]

I have written the following function :

def cand (a,b) :
   if (a) :
      if (b) :
         return true
      else :
         return false
   else :
      return false

If I (try to) call it with :

i = 'none'
limit = 5
cand (type (i) is int, i > limit)

I get an error :

TypeError: '>' not supported between instances of 'int' and 'str'

In fact the function is not called. If I put a print in it, it is not displayed.
For me it is a bug. The function must be called and the second element not evaluated before calling the function but only if requested by the function code.

CPython versions tested on:

3.13

Operating systems tested on:

Windows

[terryjreedy]

cand is not called because the argument expression, i > limit, which resolves to 'none' > 5, is a bug, giving the error message shown.

>>> 'none' > 5
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    'none' > 5
TypeError: '>' not supported between instances of 'str' and 'int'

The traceback shows which expression failed. It should be examined before reporting and included in reports if you do not see the problem.

Note that I edited your report to include code between pairs of triple backticks. Left click ... at the top of your message and select edit to see. (Adding python is optional, but gets syntax color marking.) Tracebacks should also be more this way, as I did above.

Please ask questions about bug on https://discuss.python.org/c/help/7, where more people will see the question and answer.

[choucroute1958]

From my point of view, the second argument expression may not be evaluated before the function is called, but only inside the function if requested by its code.
In this case, the "if (a) :" will resolve in "if type (i) is int :", which is False, and the function will return False without trying to evaluate the second argument.

[choucroute1958]

Is there someone following this discussion ?

[sergey-miryanov]

Is there someone following this discussion ?

Python uses call-by-value evaluation strategy - all arguments of a function call evaluated before the function is invoked. You described another strategy - call-by-need or call-by-name. If you need so - you have to take another language.

There is nothing to discuss from python point of view.