In this section, we will learn about type conversion. We've already
learned how to create different variable types in Python:
greeting = "hello"
gives us a string
answer = 42
gives us an integer
distance = 4.2
gives us a float
But what if we what to change a variable's data type? Say, for example,
we had a string "145", but we wanted to use it to do some math. As it
is now, Python won't let you do any math. If we try, we get:
var = "145"
result = var + 4
print(result)
# Traceback (most recent call last):
# File "<stdin>", line 1, in <module>
# TypeError: can only concatenate str (not "int") to str
In order to make this work, we first have to convert "145" to an
integer. We can do this using the built-in data type keywords:
str()
for string
int()
for integer
float()
for float
Let's try our example again:
var = int("145")
result = var + 4
print(result)
# 149
This is especially useful for converting input from the user from
strings to numbers:
radius = float(input("Enter a radius: "))
area = 3.14 * radius ** 2
print(f"The area of a circle with radius {radius} is {area}.")
Be careful when converting though! If your string can't be turned into
a number, because it's something like "hello" for example, your program
will give you an error!