day1 -- Python变量、注释、格式化输出字符串、input、if、while、for

1.python变量

　　不需要声明类型，直接 变量名 = 变量值，如 ： name = "hahaha"

2.注释：

　　单行注释，前面加 #，如  # print(info) 

　　多行注释，用三组单引号或者三组双引号包围起来，如   '''print(info)'''   """print(info)""" 

　　注意：三组单引号包围起来的变量可以直接格式化输出，看下面的3的第一个案例

3.格式化输出字符串

info = '''name is %s and age is %s''' % (name, age)
info2 = "name2 is {n} and age2 is {a}".format(n=name, a=age)
info3 = "name3 is {0} and age3 is {1}".format(name, age)

 4.input()方法默认输入存储的类型是str，如果需要转换类型可以使用类型转换函数如int()，如：

age = int(input("input your age:"))

5.if、elif、else：注意顶格对齐

my_age = int(input("guess my age:"))
if my_age > 60:
    print("you guess error")
elif my_age == 60:
    print("you guess right")
else:
    print("hhh")

6.while

count = 0
while count < 3:
    age = int(input("guess my age:"))
    if age < 50:
        print("sorry, your answer is error")
    elif age == 50:
        print("{a} is right".format(a=age))
        break
    else:
        print("hhh")
    count += 1
# while条件不符合，则走else里面的
else:
    print("you have tried too many times!!!")

7.for

for i in range(3):
    age = int(input("guess my age:"))
    if age < 50:
        print("sorry, your answer is error")
    elif age == 50:
        print("{a} is right".format(a=age))
        break
    else:
        print("hhh")
# for正常结束，则走else里面的，
# 如果for被break，则不走else里面的
else:
    print("you have tried too many times!!!")

　　tip：range方法看下面

8.range方法

# 起始，终点，步长，输出0,2,4,6,8
for i in range(0, 10, 2):
    print("i = ", i)

# 默认步长为 1，即输出1-99
for j in range(99):
    print(i)