初学Python(二)

一：if语句

1.判断列表里的值

cars=["dew","ed","ge","jg","bg"]
for ca in cars:
if(ca=='dew'):
print(ca.upper())
else:
print(ca.title())
DEW
Ed
Ge
Jg
Bg


2.检查特定值是否不包含在列表中

cars=["dew","ed","ge","jg","bg"]
ca="pyt"
if ca not in cars:
print('dewe' in cars)

二：使用字典

1.定义字典alien0={"pyt":5,'rym':'rym'}
print(alien0["pyt"])
5

2.添加键值对

alien0={"pyt":5,'rym':'rym'}
print(alien0["pyt"])
alien0['hji']=6
alien0['kij']=7
print(alien0)
{"pyt":5,'rym':'rym','hji':6,''kij":7}



3.修改值

alien0={"pyt":5,'rym':'rym'}
alien0['pyt']=7
print(alien0)
{"pyt":7,'rym':'rym'}

4.删除值

alien0={"pyt":5,'rym':'rym'}
del alien0['pyt']
print(alien0)
{'rym':'rym'}

5.遍历字典

alien0={"pyt":5,'rym':'rym'}
for a,b in alien0.items():
print(a+""+b)
pyt 5
rym rym

6.遍历字典中的键(按顺序)

alien0={"pyt":5,'rym':'rym'}
for a in sorted(alien0.keys()):
print(a)
pyt
rym

7.遍历字典中的值

alien0={"pyt":5,'rym':'rym'}
for a in alien0.values():
print(a)
5
rym

三：While循环

1.input()语句的应用

message=input("你是谁？")
print(message)
你是谁？panyutian
panyutian

2.while循环定义

current_number = 1
while current_number<5:
print(current_number)
current_number+=1
1
2
3
4

3.break和continue

跳出循环体和结束本次循环开始下次循环

三：函数

1.定义函数（实参/关键字实参/默认值）

def greet(name):
print(name)
greet("我们")
我们

2.返回值

def greet():
a=5
return a
greet()
5