0 Basic python-3.3 Identifiers

1. Composition of identifiers

1) There are numbers, underscores, English letter composition

2) The first character can only be a letter or an underscore

3) uppercase and lowercase sensitive

Identifiers are usually variable names, method names, class names, etc.

2.keyword

Python has a series of keywords, assuming you don't know whether a word is, you can use Iskeyword () This method to test

3. Built-in

1) can be used as a system reserved word

2) can be used as a global variable

3) The interpreter actively imports itself before Python starts

4. Dedicated underline

1) _xxx do not import from module import *

2) _xxx_ System definition Name

3) Private variables in the _xxx class

Note: Double underlines have special meanings for python, such as __ini__, which represents the initialization method of the class, followed by a lot of specific expansion

0 Basic python-3.3 Identifiers