Performance: (Compare string) vs (convert to int)

Question

Hi all: I am new to Stack Overflow and am rather new to python, but I have been writing code for years and would like to know which of the following would be better performance.

Assume I have loaded envioron from os, and the flag in the environment is guaranteed to be either a "0" or "1".

if environ["Flag"] == "1":
    do_something

or

if int(environ["Flag"]) == 1:
    do something

At first glance, it looks like the conversion to int, then comparison would be slower because of the conversion, however, I know string comparisons can be slow also.

Has anyone ever examined this?

Thanks, Mark.

Answer 1

In [44]: timeit int("1") == 1
1000000 loops, best of 3: 380 ns per loop

In [44]: timeit "1" == "1"
10000000 loops, best of 3: 36.5 ns per loop

Casting to int will always be slower which makes perfect sense, you start out with a string then convert to an int instead of just creating a string.

Converting is the most costly part:

In [45]: timeit 1
100000000 loops, best of 3: 11.9 ns per loop

In [46]: timeit "1" 
100000000 loops, best of 3: 11 ns per loop

In [47]: timeit int("1")
1000000 loops, best of 3: 366 ns per loop

There is a difference between creating a string using a = "1" than doing a = 1 b = str(1) which is where you may have gotten confused`.

In [3]: a = 1

In [4]: timeit str(b)
10000000 loops, best of 3: 135 ns per loop

timed using python2.7, the difference using python 3 is pretty much the same.

The output is from my ipython terminal using the ipython magic timeit function