python | Variable

Form

python variables generated without prior notice, the system according to the assignment operator or automatically infer variable type.

x = 123
type(x)     # 数值型变量

y = '123'
type(y)     # 数值型变量

Storage

python using " memory-based value management ", in essence, save variable values at the memory address, rather than the value itself.

# 多个变量指向同一个地址
x = 3
id(x)
y = 3
id(y)

modify

python with " assignment modifications" variables, that is, the specific =right value assigned to variable on the left, is essentially a modified memory address variable points.
Note that the variable part of the definition of a variable name appears for the first time, but again belongs modify variables

x = 321
type(x)     # 定义一个变量

x = 'abc'
type(x)     # 赋值修改变量

name

The general principle is named " All names must be meaningful, at a glance ."

• Naming of
  • Allow case letters, numbers, underline, and combinations thereof
  • The first character can not be a number, and is case sensitive
  • Underlined _achieve intervals, such as first_name, can not be other symbols, and spaces
  • Caution lowercase land uppercase letters O, as is easily mistaken for digital 1and0
  • Reserved word or not, and the same functions built python
    
• Naming
  • Small hump nomenclature: more words variables, the first letter lowercase first letter of each word in the back of the first word is capitalized. Such asmyFirstName
  • Large hump nomenclature: also known as "Pascal's nomenclature," that the first letter of all words require capitalization. Such as Person,MyLastName
  • Underline nomenclature: underlined _achieve interval, such asfirst_name

from IPython.core.interactiveshell import InteractiveShell
InteractiveShell.ast_node_interactivity = 'all'

my_age = 1
id(my_age)                        # 定义一个变量my_age
my_age = 2
id(my_age)                        # 给变量my_age重新赋值后，my_age指向的内存地址发生改变

SeatNum1, SeatNum2 = 88, 99       # 可以同时给多个变量赋值