How to Get the Length of an Integer in Python?

You can get the length of an integer in Python in any of the following ways:

• Converting to String and Checking the Length;
• Converting to list and Checking the Length;
• Looping and Removing Digits Off the End;
• Calculating the Number of Digits.

Converting to String and Checking the Length

If you have a positive integer, you can do the following:

1. Convert integer to string (using str());
2. Call the len() method on the resulting string.

num = 12345
num_str = str(num)
print(len(num_str)) # 5

If the number can potentially be negative, then you must first get the absolute value of the integer:

num = -12345
num_str = str(abs(num))
print(len(num_str)) # 5

To make it reusable, you could make this into a function, for example, like so:

def num_length(num):
    return len(str(abs(num)))

print(num_length(0)) # 1
print(num_length(12345)) # 5
print(num_length(-12345)) # 5
print(num_length(9999999999999999999999999)) # 25
print(num_length(-9999999999999999999999999)) # 25

Converting to list and Checking the Length

If you have a positive integer, you can do the following:

1. Convert integer to a list of digits;
2. Call the len() method on the resulting list of digits.

For example, you can do this using list comprehension like so:

num = 12345
digits = [int(x) for x in str(num)]
print(len(digits)) # 5

You can rewrite the same code using map() like so:

num = 12345
digits = list(map(int, str(num)))
print(len(digits)) # 5

If the number can potentially be negative, then you must first get the absolute value of the integer:

num = -12345
digits = [int(x) for x in str(abs(num))]
print(len(digits)) # 5

To make it reusable, you could make this into a function, for example, like so:

def num_length(num):
    digits = [int(x) for x in str(abs(num))]
    return len(digits)

print(num_length(0)) # 1
print(num_length(12345)) # 5
print(num_length(-12345)) # 5
print(num_length(9999999999999999999999999)) # 25
print(num_length(-9999999999999999999999999)) # 25

Looping and Removing Digits Off the End

If you have a positive or a negative integer, you can do the following:

1. Create a loop, and remove the last digit from the number in each iteration till there are no digits left;
2. In each iteration, increment a counter, which would give the total number of digits in the number.

def num_length(num):
    num = abs(num)
    length = 0

    while True:
        length += 1
        num = num // 10

        if num == 0:
            break

    return length

print(num_length(0)) # 1
print(num_length(12345)) # 5
print(num_length(-12345)) # 5
print(num_length(9999999999999999999999999)) # 25
print(num_length(-9999999999999999999999999)) # 25

Calculating the Number of Digits

You should use this method with caution as it may give you the wrong result for really large numbers (such as 9999999999999999999999999).

If you have a positive integer, you can do the following:

1. Calculate the log10 of the number, convert it to an integer and add 1 to the result;
2. If the number is 0, then return 1 as a count (because log10(0) equals -inf).

import math

num = 12345
length = 1 if num == 0 else int(math.log10(num)) + 1

print(length) #=> 5

If the number can potentially be negative, then you must first get the absolute value of the integer:

import math

num = -12345
length = 1 if num == 0 else int(math.log10(abs(num))) + 1

print(length) #=> 5

To make it reusable, you could make this into a function, for example, like so:

import math

def num_length(num):
    return 1 if num == 0 else int(math.log10(abs(num))) + 1

print(num_length(0)) # 1
print(num_length(12345)) # 5
print(num_length(-12345)) # 5

// this may give wrong result for really large numbers
print(num_length(9999999999999999999999999)) # 26
print(num_length(-9999999999999999999999999)) # 26