Python Program to Count Number of Digits

You can count the number of digits in an integer in Python by converting it to a string and using len(str(abs(number))) to get the count.

Examples

Input12345

Output5

Input-987654321

Output9

Input0

Output1

How to Think About It

To count digits, first ignore if the number is negative by taking its absolute value. Then convert the number to a string so each digit becomes a character. Finally, count how many characters are in that string using length.

Algorithm

1

Get the input number.

2

Convert the number to its absolute value to ignore negative sign.

3

Convert the absolute number to a string.

4

Count the length of the string to find the number of digits.

5

Return or print the count.

Code

python

number = int(input("Enter an integer: "))
count = len(str(abs(number)))
print("Number of digits:", count)

Output

Enter an integer: 12345
Number of digits: 5

Dry Run

Let's trace the input 12345 through the code

1

Input number

number = 12345

2

Absolute value

abs(number) = 12345

3

Convert to string

str(abs(number)) = '12345'

4

Count length

len('12345') = 5

5

Print result

Output: Number of digits: 5

Step	Value
Input number	12345
Absolute value	12345
String conversion	'12345'
Length count	5

Why This Works

Step 1: Handle negative numbers

Using abs() removes the negative sign so it doesn't count as a digit.

Step 2: Convert to string

Converting the number to a string lets us treat each digit as a character.

Step 3: Count characters

Using len() on the string gives the total number of digits.

Alternative Approaches

Using a loop and integer division

python

number = int(input("Enter an integer: "))
num = abs(number)
count = 0
if num == 0:
    count = 1
else:
    while num > 0:
        num //= 10
        count += 1
print("Number of digits:", count)

This method counts digits by dividing the number repeatedly by 10. It avoids string conversion but is longer.

Using logarithm

python

import math
number = int(input("Enter an integer: "))
num = abs(number)
if num == 0:
    count = 1
else:
    count = int(math.log10(num)) + 1
print("Number of digits:", count)

This method uses math.log10 to find digit count quickly but requires import and careful zero handling.

Complexity: O(n) time, O(n) space

Time Complexity

Converting the number to a string takes time proportional to the number of digits, so O(n).

Space Complexity

The string conversion uses extra space proportional to the number of digits, so O(n).

Which Approach is Fastest?

The string method is simple and fast for typical use. The loop method is also O(n) but more verbose. The logarithm method is fastest mathematically but needs extra care.

Approach	Time	Space	Best For
String conversion	O(n)	O(n)	Simplicity and readability
Loop with division	O(n)	O(1)	Avoiding string conversion
Logarithm method	O(1)	O(1)	Mathematical efficiency with care