python入门二

一、流程控住之if判断
语法1
if 条件:
代码1
代码2
代码3】
...

cls='human'
sex='female'
age=18

if cls == 'human' and sex == 'female' and age > 16 and age < 22:
print('开始表白')

print('end....')

语法2
if 条件:
代码1
代码2
代码3
...
else:
代码1
代码2
代码3
...

cls='human'
sex='female'
age=38

if cls == 'human' and sex == 'female' and age > 16 and age < 22:
print('开始表白')
else:
print('阿姨好')

print('end....')

语法3
if 条件1:
代码1
代码2
代码3
...
elif 条件2:
代码1
代码2
代码3
...
elif 条件3:
代码1
代码2
代码3
...
............
else:
代码1
代码2
代码3
...

'''
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('your score: ') #score='73'
score=int(score) #score=73
if score >= 90:
print('优秀')
elif score >= 80:
print('良好')
elif score >= 70:
print('普通')
else:
print('很差')

user_from_db='egon'
pwd_from_db='123'

user_from_inp=input('username>>>: ')
pwd_from_inp=input('password>>>: ')

if user_from_inp == user_from_db and pwd_from_inp == pwd_from_db:
print('login successfull')
else:
print('user or password error')

if的嵌套

cls='human'
sex='female'
age=18
is_success=False

if cls == 'human' and sex == 'female' and age > 16 and age < 22:
print('开始表白...')
if is_success:
print('在一起')
else:
print('我逗你玩呢....')
else:
print('阿姨好')

print('end....')

二、流程控制之while循环
while语法,while循环又称为条件循环
while 条件:
code1
code2
code3
....

user_db='egon'
pwd_db='123'

while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
else:
print('user or password error')

2 while+break:break的意思是终止掉当前层的循环,.执行其他代码
while True:
print('1')
print('2')
break
print('3')

user_db='egon'
pwd_db='123'

while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
break
else:
print('user or password error')

print('其他代码')

3 while+continue:continue的意思是终止掉本次循环,.直接进入下一次循环
ps:记住continue一定不要加到循环体最后一步执行的代码
n=1
while n <= 10: #
if n == 8:
n += 1 #n=9
continue
print(n)
n+=1 #n=11

while True:
if 条件1:
code1
code2
code3
continue #无意义
elif 条件1:
code1
continue #有意义
code2
code3
elif 条件1:
code1
code2
code3
continue #无意义
....
else:
code1
code2
code3
continue #无意义

while循环嵌套
user_db='egon'
pwd_db='123'

while True:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
while True:
cmd=input('请输入你要执行的命令: ')
if cmd == 'q':
break
print('%s 功能执行...' %cmd)
break
else:
print('user or password error')

print('end....')

#while+tag
user_db='egon'
pwd_db='123'

tag=True
while tag:
inp_user=input('username>>: ')
inp_pwd=input('password>>: ')
if inp_user == user_db and inp_pwd == pwd_db:
print('login successfull')
while tag:
cmd=input('请输入你要执行的命令: ')
if cmd == 'q':
tag=False
else:
print('%s 功能执行...' %cmd)

else:
print('user or password error')

print('end....')

#while+else (***)
n=1
while n < 5:
# if n == 3:
# break
print(n)
n+=1
else:
print('在整个循环结束后,会进行判断:只有while循环在没有被break结束掉的情况下才会执行else中的代码')

三、流程控制之for循环
names=['egon','asb','wsb','lsb','csb']

n=0
while n < len(names):
print(names[n])
n+=1

names=['egon','asb','wsb','lsb','csb']
info={'name':'egon','age':18,'sex':'male'}

for k in info: #x=''age'
print(k,info[k])

# for item in names:
# print(item)

for i in range(1,10):
print(i)

for i in range(10): #默认的起始位置是0
print(i)

for i in range(1,10,2): #1 3 5 7 9
print(i)

names=['egon','asb','wsb','lsb','csb']
for i in range(len(names)):
print(i,names[i])

for i in range(5):
print('========>第一层: %s<=========' %i)
for j in range(3):
print(' 第二层: %s' %j)

for+break
names=['asb','wsb','egon','lsb','csb']
for n in names:
if n == 'egon':
break
print(n)

for+continue
names=['asb','wsb','egon','lsb','csb']
for n in names:
if n == 'egon':
continue
print(n)

#for+else
names=['asb','wsb','egon','lsb','csb']
for n in names:
# if n == 'egon':
# break
print(n)
else:
print('=====>')