Python type() function: why 3, 3.0 and "3" are different
Three values that look alike are an int, a float and a str. type() shows the difference, and mixing them shows why it matters.
Three, three point zero, and three in quotes look alike. Python knows they are three different data types, and the type() function shows you which is which. You never had to say so.
Ask it with type()
print(type(3))
print(type(3.0))
print(type("3"))
print(type(True))
print(type(None))<class 'int'>
<class 'float'>
<class 'str'>
<class 'bool'>
<class 'NoneType'>3 is an int, a whole number. 3.0 is a float. "3" is a str, text. True is a bool, and None is its own type. You never declared any of this: Python worked it out from the value.
It matters when you mix them
>>> 3 + 3.0
6.0
>>> 3 + "3"TypeError: unsupported operand type(s) for +: 'int' and 'str'A number plus a float gives a float. A number plus text is an error, because Python will not guess whether you wanted 6 or "33". Convert first, and say which:
>>> int("3") + 3
6
>>> str(3) + "3"
'33'What to take from this
- The type is in the value. A name has no type of its own.
type(x)tells you what Python sees.- Values of different types do not combine by themselves. Convert with
int(),float()orstr()first.
This is a short note on Variables and types, lesson 2 of the Python beginner track.
This article goes with the video Python knows the type. Watch it on YouTube.