[Python-Dev] bpo-36558: Change time.mktime() return type from float to int? (original) (raw)

Ivan Pozdeev vano at mail.mipt.ru
Tue Apr 16 11:47:35 EDT 2019

On 16.04.2019 17:24, Victor Stinner wrote:

Hi,

time.mktime() looks "inconsistent" to me and I would like to change it, but I'm not sure how it impacts backward compatibility. https://bugs.python.org/issue36558 time.mktime() returns a floating point number:

type(time.mktime(time.localtime())) <class 'float'> The documentation says: "It returns a floating point number, for compatibility with :func:.time." time.time() returns a float because it has sub-second resolution, but the C function mktime() returns an integer number of seconds. Would it make sense to change mktime() return type from float to int? I would like to change mktime() return type to make the function more consistent: all inputs are integers, it sounds wrong to me to return float. The result should be integer as well. How much code would it break? I guess that the main impact are unit tests relying on repr(time.mktime(t)) exact value. But it's easy to fix the tests: use int(time.mktime(t)) or "%.0f" % time.mktime(t) to never get ".0", or use float(time.mktime(t))) to explicitly cast for a float (that which be a bad but quick fix). I envision it breaking code that relies on implicitly inferring the type of the result from the types of both operands (e.g. arithmetic operations). But for mktime() specifically, I presume the amount of such code very small. Note: I wrote and implemented the PEP 564 to avoid any precision loss. mktime() will not start loosing precision before year 285,422,891 (which is quite far in the future ;-)). Victor

-- Regards, Ivan

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