流程控制之循环
作者：互联网
今日内容：
1、流程控制之if判断
2、流程控制之循环
while循环-》“条件循环”
for循环-》“取值循环”
流程控制即控制流程，具体指控制程序的执行流程
1、什么是if判断
接收用户输入的用户名
接收用户输入的密码
判断 输入的用户名 等于 正确的用户名 并且 输入的密码 等于 正确的密码:
告诉用户登录成功
否则:
告诉用户登录失败
2、为何要用if判断
为了让计算机能够像人一样去判断
3、如何用if判断
一 if判断基本运行原理解析,完整语法
if 条件1:
子代码
elif 条件2:
子代码
elif 条件3:
子代码
......
else:
子代码
二：单分支
gender = "female"
age = 27
is_beautiful = True
if gender == "female" and 18 < age < 26 and is_beautiful:
print("我喜欢，加个微信")
print('end.....')
三：双分支
gender = "female"
age = 27
is_beautiful = True
if gender == "female" and 18 < age < 26 and is_beautiful:
print("我喜欢，加个微信")
else:
print("咱俩不太合适")
print('end.....')
案例：
inp_user = input("请输入您的用户名：")
inp_pwd = input("请输入您的密码：")
if inp_user == "egon" and inp_pwd == "123":
print("登录成功")
else:
print("登录失败")
四：多分支
如果：成绩>=90，那么：优秀
如果成绩>=80且<90,那么：良好
如果成绩>=70且<80,那么：普通
其他情况：很差
score = input("请输入您的分数 ")
score = int(score)
if score >= 90:
print("优秀")
elif score >= 80:
print("良好")
elif score >= 70:
print("普通")
else:
print("很差")
gender = 'female'
age = 19
is_beautiful = True
if gender == 'female' and 18 < age < 25 and is_beautiful:
print('加个微信')
inp_user = input('用户名')
inp_pwd = input('密码')
if inp_user == 'xxx' and inp_pwd == '123':
print('登陆成功')
else:
print('用户名或者密码错误')
score = input('请输入您的分数')
score = int(score)
if score >= 90:
print('优秀')
elif score >= 80:
print('良好')
elif score >= 70:
print('普通')
else:
print('很差')
i = 1
while i <= 5:
print(i)
i += 1
i = 1
tag = True
while tag:
if i == 5:
tag = False
print(i)
i += 1
i = 1
tag = True
while tag:
if i == 5:
break
print(i)
i += 1
i = 1
while i <= 5 :
print(i)
i += 1
num = 11
while num > 1:
num -= 1
if num == 7:
continue
print(num)
tag = True
while tag:
username = input('请输入账号')
password = input('密码')
if username == 'xxx' and password == '123':
print('登陆成功')
tag = False
else:
print('登陆失败')
print('....')
while True:
username = input('请输入账号')
password = input('密码')
if username == 'xxx' and password == '123':
print('登录成功')
break
else:
print('登陆失败')
print('....')
i = 1
while i <= 5:
if i == 3:
i += 1
continue
print(i)
i += 1
nums = [111, 222, 333, 444, 555]
i = 0
while i < len(nums):
print(nums[i])
i += 1
nums = [111, 222, 333, 444, 555]
for i in nums:
print(i)
dic = {'k1': 111, 'k2': '222', 'k3': 333}
for x in dic:
print(x, dic[x])
for i in range(1,100):
print(i)
一 for更擅长遍历值,for循环的次数取决值的个数
nums = [111, 222, 333, 444, 555]
i = 0
while i < len(nums):
print(nums[i])
i += 1
for num in nums: # num = 222
print(num)
for x in "hello":
print(x)
dic = {'k1':111,'k2':222,'k3':333}
for k in dic:
print(k,dic[k])
items = [['name', "egon"], ['age', 18], ['gender', "male"]]
for x,y in items: # x,y = ['name', 'egon']
print(x,y)
二 for+break
nums = [111, 222, 333, 444, 555]
for num in nums:
if num == 333:
break
print(num)
三 for+continue
nums = [111, 222, 333, 444, 555]
for num in nums:
if num == 333:
continue
print(num)
四 for+else
nums = [111, 222, 333, 444, 555]
for num in nums:
if num == 333:
# break
continue
print(num)
else:
print('======')
五
让某段代码重复运行3次-》while循环实现如下
i = 0
while i < 3:
print('hello1')
print('hello2')
print('hello3')
i += 1
让某段代码重复运行3次-》for循环实现如下
for x in range(3):
print('hello1')
print('hello2')
print('hello3')
for x in range(100):
print(x)
六 for+enumerate
nums = [111, 222, 333, 444, 555]
i = 0
while i < len(nums):
print(i,nums[i])
i += 1
for i,num in enumerate(nums):
print(i,num)
标签：控制,num,nums,流程,333,else,循环,print,input 来源： https://www.cnblogs.com/echoxkx/p/15079578.html