Length of an integer in Python


In Python, how do you find the number of digits in an integer?

9/2/2016 6:40:55 PM

Accepted Answer

If you want the length of an integer as in the number of digits in the integer, you can always convert it to string like str(133) and find its length like len(str(123)).

3/23/2013 2:19:29 AM

Without conversion to string

import math
digits = int(math.log10(n))+1

To also handle zero and negative numbers

import math
if n > 0:
    digits = int(math.log10(n))+1
elif n == 0:
    digits = 1
    digits = int(math.log10(-n))+2 # +1 if you don't count the '-' 

You'd probably want to put that in a function :)

Here are some benchmarks. The len(str()) is already behind for even quite small numbers

timeit math.log10(2**8)
1000000 loops, best of 3: 746 ns per loop
timeit len(str(2**8))
1000000 loops, best of 3: 1.1 µs per loop

timeit math.log10(2**100)
1000000 loops, best of 3: 775 ns per loop
 timeit len(str(2**100))
100000 loops, best of 3: 3.2 µs per loop

timeit math.log10(2**10000)
1000000 loops, best of 3: 844 ns per loop
timeit len(str(2**10000))
100 loops, best of 3: 10.3 ms per loop

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