Python int() Function

The int() function in Python converts a number or a string into an integer. It's one of the most commonly used functions in Python programming.

Syntax

int(x=0, base=10)

Parameters:

• x – A number (like float or string) to convert to an integer. Default is 0.
• base – (Optional) The base of the number (used only if x is a string). Default is 10.

Returns:

• An integer representation of the input.

Example 1: Convert Float to Integer

print(int(5.9))

5

Note: It truncates the decimal part (does not round).

Example 2: Convert String to Integer

print(int("42"))

42

Example 3: Convert Binary String to Integer

print(int("101", 2))

5

Example 4: Convert Hexadecimal String to Integer

print(int("1A", 16))

26

Use Cases

• Converting user input (strings) into usable numeric values
• Truncating float values into whole numbers
• Converting from binary, octal, or hexadecimal to decimal

Common Mistakes

• Passing a string with letters in base 10: int("abc") → ValueError
• Using invalid bases (must be between 2 and 36)
• Passing None or an empty string: causes TypeError or ValueError

Interview Tip

The int() function is frequently used in string parsing, input handling, and base conversions — all common in coding interviews.

Summary

• int() converts numbers and strings to integers.
• If a float is passed, it truncates the decimal part.
• If a string is passed with a base, it converts from that base.

Practice Problem

Write a program that asks the user to enter a number and prints the number as an integer.

user_input = input("Enter a number: ")
try:
    print("As integer:", int(user_input))
except ValueError:
    print("That's not a valid number!")