Type Conversion

4.1 The int() Function

In Python, type conversion (also called type casting) lets you convert values from one data type to another. We've briefly touched on converting a string to a number during input, but now let's dive deeper into this topic. Let's check out the three main functions for type conversion: int(), str(), and float().

The int() function is used to convert a value to an integer.

Converting a string to an integer:

num_str = "42"
num_int = int(num_str)
print(num_int)  # Output: 42
    

You'll get an error if the string isn't a number:

num_str = "forty two"
num_int = int(num_str)
print(num_int)  # ValueError: invalid literal for int() with base 10: 'forty two'

Converting a floating-point number to an integer:

num_float = 42.9
num_int = int(num_float)
print(num_int)  # Output: 42

Rounding down always happens in such conversions — only the integer part of the number is kept. For example, 1.9999 will give 1.

Converting a boolean value to an integer:

A true value (True) is often called a "logical one," and a false value (False) is a "logical zero." After conversion, they become regular one and zero respectively.

true_bool = True
false_bool = False
print(int(true_bool))  # Output: 1
print(int(false_bool))  # Output: 0

4.2 The str() Function

The str() function is used to convert values to strings. Pretty much anything can be converted into a string.

Converting an integer to a string:

num_int = 42
num_str = str(num_int)
print(num_str)  # Output: "42" 

Converting a floating-point number to a string:

num_float = 42.9
num_str = str(num_float)
print(num_str)  # Output: "42.9" 

Converting a boolean value to a string:

true_bool = True
false_bool = False
print(str(true_bool))  # Output: "True"
print(str(false_bool))  # Output: "False" 

4.3 The float() Function

The float() function is used to convert a value to a floating-point number (a decimal number).

Converting a string to a floating-point number:

num_str = "42.9"
num_float = float(num_str)
print(num_float)  # Output: 42.9 

Converting an integer to a floating-point number:

num_int = 42
num_float = float(num_int)
print(num_float)  # Output: 42.0  

Converting a boolean value to a floating-point number:

true_bool = True
false_bool = False
print(float(true_bool))  # Output: 1.0
print(float(false_bool))  # Output: 0.0 

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