This series of essays is my study notes, beginner stage will inevitably be understood inappropriate, wrong place kindly correct me. Please indicate the source: https://www.cnblogs.com/itwhite/p/12297694.html .
constant
Python and does not provide as C / C ++ in as the const keyword from the definition of constants, so in addition to literals, python says this is not constant.
Each data type has a corresponding literal, for example:
| type of data | Literals example |
|---|---|
| Integer | 123、-456 |
| Float | 3.14 |
| Boolean | True、False |
| None | None |
| String type | 'foo'、"bar"、'''qux'''、"""quz""" |
| List Type | [1, 2, 3]、["Jack", "Bob", "Lucy"] |
| Tuple type | (1, 2, 3, [4, 5, 6]) |
| Dictionary Type | { "name": "Jack", "age": 23 } |
variable
Python, no separate variable declaration, it will be automatically assigned in the first declaration (i.e., the assignment statement can not be used before unassigned), for example:
123 = foo Print (foo) # 123 Print (bar) # NameError: name 'bar' IS Not defined, can not be used before it is assigned bar = 456
Variable scope
Python variables are also points of global and local variables, unless you use the global keyword stated otherwise, when a local variable with the same name as global variables, global variables will be covered, such as:
# - * - Coding: UTF-. 8 - * - X = 123 # global variables Y = 456 # global variables Z = 789 # global variable DEF foo (A, B): Print (X) # 123, used herein are global variable X Y = a + B # assignment statement i.e., where local variables declared equivalent Y Print ( " Y: D% " % (Y)) # 33 is global Z # explicitly declared global variables Z Z = a + B # where z is a global variable is still Print ( " z: D% " % (z)) # 33 is foo ( . 11, 22 is ) Print ( " X: D% " % (X)) # 123 Print ( " y: D% " % (y)) # 456, the value of the global variable y unmodified Print ( " Z: D% " % (z)) # 33 is, the value of the global variable z is changed
Finish.