Values, Types, Variable Names, and Keywords
Read these examples of using the 'print' and 'type' functions. You can also try to use them in the Repl.it command line.
A value is one of the basic things a program works with, like a letter or a number.
These values belong to different types:
2 is an integer, and
'Hello, World!' is a string, so-called because it contains a
"string" of letters. You (and the interpreter) can identify strings because they are enclosed in quotation marks.
If you are not sure what type a value has, the interpreter can tell you.
>>> type('Hello, World!') <type 'str'> >>> type(17) <type 'int'>
Not surprisingly, strings belong to the type
str and integers belong to the type
int. Less obviously, numbers with a decimal point belong to a type called
because these numbers are represented in a format called floating-point.
>>> type(3.2) <type 'float'>
What about values like
'3.2'? They look like numbers, but they are in quotation marks like strings.
>>> type('17') <type 'str'> >>> type('3.2') <type 'str'>
When you type a large integer, you might be tempted to use commas between groups of three digits, as in
1,000,000. This is not a legal integer in Python, but it is legal:
>>> 1,000,000 (1, 0, 0)
Well, that's not what we expected at all! Python interprets
1,000,000 as a comma-separated sequence of integers. This is the first example we have seen of a semantic error: the code runs without producing an error message, but it doesn't do the "right" thing.
Source: Allen B. Downey, http://www.greenteapress.com/thinkpython/html/thinkpython003.html
This work is licensed under a Creative Commons Attribution 4.0 License.