Chapter2 Python基础
2.1 变量命名规则
- 字母、数字、下划线组成
- 不能数字开头
- 不能使用python中的关键字
- 变量名具有意义
- 推荐驼峰(ArvinGood)、或者下划线方式 (arvin_good) 命名
标准示例:
your_name = 'Jack Ma'
2.2 常量
- 全部大写的变量名就是常量 ARVIN = 99
示例:
ARVIN_AGE = 18
2.3 注释
- 三种方式:
- “#”号单行注释
- ‘’‘三个单引号和三个双引号”“”进行多行注释
例:
# The idle boy is almost invariably poor and anxious. 单行注释
'''
这是多行注释示范
'''
"""
多行注释示范
"""
2.4 输入输出
- 用户输入 input
- 注意:input获取到的内容都是字符串类型
- 用户输出 print
- print打印出内容
your_id = input("input your id identifier: ")
your_pwd = input("input your password: ")
print("Your id is {}, Your password is {}".format(your_id, your_pwd))
运行结果:
input your id identifier: Jack
input your password: default
Your id is Jack, Your password is default
2.5 五种if条件判断语句
-
单if条件判断
if 条件: #条件判断 > < ==
print(‘真实’) #条件成立则执行
if 10 > 8: print("You are right.")
-
if else条件判断
if 10 > 20: print("10 is bigger than 2.") else: print("10 is smaller than 2.")
-
if elif elif else 条件判断
a = "jack" if 10 > 50: print("10 is bigger than 5.") elif type(a) == "str": print("a is a string.") elif 20 == 20: print("20 is equal 20.") else: print("All of them are false.") 运行结果: 20 is equal 20.
-
多个同级if语句
a = "jack" if 10 == 20: print("10 is equal 20.") if a == "jack": print(a ,"is the same as jack.") if 10 == 10: print("10 is equal 10.") 运行结果: jack is the same as jack. 10 is equal 10.
-
if与if语句之间的嵌套
id = int(input("input your id number: ")) pwd = input("input your passwrd: ") if id == 9: print("GO ON.") if pwd == "default": print("You logged in successfully.") else: print("Your password is incorrect.") else: print("Your id was typed incorrectly.")