1.5: Values and types

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A value is one of the basic things a program works with, like a letter or a number. Some values we have seen so far are 2, 42.0, and 'Hello, World!'.

These values belong to different types: 2 is an integer, 42.0 is a floating-point number, and 'Hello, World!' is a string, so-called because the letters it contains are strung together.

If you are not sure what type a value has, the interpreter can tell you:

>>> type(2)
<class 'int'>
>>> type(42.0)
<class 'float'>
>>> type('Hello, World!')
<class 'str'>

In these results, the word “class” is used in the sense of a category; a type is a category of values.

Not surprisingly, integers belong to the type int, strings belong to str and floating-point numbers belong to float.

What about values like '2' and '42.0'? They look like numbers, but they are in quotation marks like strings.

>>> type('2')
<class 'str'>
>>> type('42.0')
<class 'str'>

They’re strings.

When you type a large integer, you might be tempted to use commas between groups of digits, as in 1,000,000. This is not a legal integer in Python, but it is legal:

>>> 1,000,000
(1, 0, 0)

That’s not what we expected at all! Python interprets 1,000,000 as a comma-separated sequence of integers. We’ll learn more about this kind of sequence later.