I already chimed in on the issue, but for the list, I'll boil my comments down to two questions:

1. For anyone who knows: when the documentation refers to "compatibility with `.time`", is that just saying it was designed that way because .time returns a float (i.e. for /consistency/ with `.time()`), or is there some practical reason that you would want `.time()` and `.mktime()` to return the same type?

2. Mainly for Victor, but anyone can answer: I agree that the natural output of `mktime()` would be `int` if I were designing it today, but would there be any /practical/ benefits for making this change? Are there problems cropping up because it's returning a float? Is it faster to return an integer?

Best,

Paul

On 4/16/19 10:24 AM, 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).

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

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.

In C, the signature of mktime is time_t mktime(struct tm *time); from Wikipedia, the Unix time_t data type, on many platforms, is a signed integer, tradionally (32bits). In the newer operating systems, time_t has been widened to 64 bits.