变量和赋值
例:
name = “hong wei” #给name赋值
age = 21 #给age赋值
print(name,age)
结果:hong wei 21
例:
name = hongwei
age = 21
print(name,age)
结果:报错 SyntaxError: invalid syntax #(name = hongwei 会将hongwei本身当个变量,但是hongwei没有赋值)
改:
hongwei = "TEST"
name = hongwei
age =21
print(name,age)
结果:TEST 21
例:
a = 3
b = a
print(a,b)
print(id(a),id(b))
a = 5
print(a,b)
print(id(a),id(b))
结果:
3 3
1571182896 1571182896
5 3
1571182928 1571182896
#(a = 3 给a赋值一个3;b = a 把a 的值赋值给b (b指向的是a指向的地址,也就是3);a = 5 (a改名了3就被python解释器回收,但是b还是指向3,所以pthon解释器看到有人指向3,就不会回收3,所有b输出结果为3,a就为5))
给变量起名:
1.显式(名字要通俗易懂)
2.硬性规则
1.(nums_of_hongwei_gf = 19)
2.NumsOfHongweiGF = 2
不合法:
1.names -of-hongwei-gf = 2(变量由字母、数字、下划线组成)
2.5name (数字不能开头)
3.!name(特殊字符不能开头)
4.hong wei (不能有空格)
5.关键字不能为变量(‘and’,'as','assert','break','class','contine','del','elif','else','else','except','exec','finally','for','from','global',
'if','import','in','is','lambda','not','or','pass','print','raise','return','try','while','with','yield')