In Python, and in most programming languages, the value 123 is a very different thing to the string “123”
The first is a number that you can use in calculations. The second is some text: you can’t use it in calculations.
A common thing to do is convert text representing a number to an actual number, or the opposite: we might want to convert a number to text so we can use string methods on it.
We can also convert one kind of number to another; for example, we can convert an integer to a floating point number.
Simple conversions like these are often called casts. The conversion is known as casting.
We can perform a cast using one of several built-in Python functions. The most important functions used in this way are:
- int() — convert to an integer
- float() – convert to a floating-point number
- str() — convert to a string
Casting: Some Examples
value = "123" print(type(value)) # Convert the string to an integer # using the int() builtin function. # Then assign the result back to # the original variable. value = int(value) print(type(value)) # Now convert to a float instead. value = float(value) print(type(value)) # And back to a string. value = str(value) print(type(value))
<class 'str'> <class 'int'> <class 'float'> <class 'str'>
In the next article we’ll use casting to help implement a program that converts a temperature in Fahrenheit to a temperature in Celsius.