一、if判断
python中使用缩进来区分代码块
语法:
1、if 条件:
子代码块
2、if 条件:
条件成立执行代子码块
子代码块
else:
条件不成立执行代子码块
子代码块
练习:
sex = "female"
age = 18
is_beatuiful = True
is_successful = True
height = 1.70
if sex == "female" and age >16 and age <24 and is_beatuiful and height > 1.60 and height <1.8:
print("开始表白")
if is_successful:
print("在一起。。。")
else:
print("什么狗屁爱情")
else:
print("独自深夜买醉")
3、套嵌
if 条件:
if 条件:
else:
else:
4、if 条件一:
elif:条件二:
else:
练习:
学生输入成绩,对学生成绩进行评价 [90-100] 为优秀,[80,90)为良好,
[70,80)为普通,低于七十分为很差。
grades = int(input("请输入你的成绩>>>"))
if grades >= 90:
print('优秀')
elif grades >= 80:
print('良好')
elif grades >= 70:
print('普通')
else:
print('很差')
二、while循环
千万不要在while循环中写带有运算类的代码:
示例:
while True:
name = input("pleasse input your name: ")
pwd = input("pleasse input your pwd")
if name == "song" and pwd == "123"
print("log in success")
else:
print("Username or password is inconrrect")
结束方式1:条件改为False
在条件改为False是不会立即结束掉循环,而是要等到下一次循环判断条件时才会生效
示例:
tag=True
while tag:
name=input("please input your name: ")
pwd=input("please input your pwd: ")
if name == "song" and pwd == "123"
input("login successful")
tag=False
else:
print("username or password errror")
print("11111111")
结束方式2:while+break
break一定要放在循环体内,一旦循环体执行到break就会立即结束本层循环
示例:
while True:
name = input("please input your name: ")
pwd = input("please input youer pwd: ")
if name == "song" and pwd == "123":
print("login successful")
break
else:
print("username or passwoed error")
print("1111111")
结束方式3:while+continue:结束本次循环,进入下一次循环
示例1:
count = 1
while count < 6
if count == 4
count += 1
continue
print("count")
count += 1
示例2:
while True:
name = input("please input your name: ")
pwd = input("please input your name")
if name == "song" and pwd == "123"
print("login successful")
break
else:
print("Username or password error")
continue 此处加continue无用
3、for循环
for循环能做的事while循环都能做,for循环的强大之处在于循环取值。
l=["a","b","c","d","e",]
用while取值步骤:
i=0
while i < len(i):
print(l[i])
i +=1
而for的取值步骤:
for x in l:
print(x)
for+range
range的用法:
range(1,5)=range(1,5,1)=range[1,2,3,4]
for i in range(1,5):
print(i)
会得出结果:1 2 3 4