python列表补充、循环

优先掌握部分
　
　　　　切片
l=['a','b','c','d','e','f']

print(l[1:5])
print(l[1:5:2])
print(l[2:5])
print(l[-1])


了解
print(l[-1:-4])
print(l[-4:])
l=['a','b','c','d','e','f']
print(l[-2:])

追加
hobbies=['play','eat','sleep','study']
hobbies.append('girls')
print(hobbies)

　　　　删除
hobbies=['play','eat','sleep','study']
x=hobbies.pop(1) #不是单纯的删除，是删除并且把删除的元素返回，我们可以用一个变量名去接收该返回值
print(x)
print(hobbies)

x=hobbies.pop(0)
print(x)

x=hobbies.pop(0)
print(x)

队列：先进先出
queue_l=[]
入队
queue_l.append('first')
queue_l.append('second')
queue_l.append('third')
print(queue_l)
出队
print(queue_l.pop(0))
print(queue_l.pop(0))
print(queue_l.pop(0))


堆栈:先进后出，后进先出
l=[]
入栈
l.append('first')
l.append('second')
l.append('third')
出栈
print(l)
print(l.pop())
print(l.pop())
print(l.pop())

了解
del hobbies[1] 单纯的删除
hobbies.remove('eat') 单纯的删除，并且是指定元素去删除


　　　　长度
hobbies=['play','eat','sleep','study']
print(len(hobbies))

　　　　包含in
hobbies=['play','eat','sleep','study']
print('sleep' in hobbies)

msg='hello world egon'
print('egon' in msg)


掌握部分
hobbies=['play','eat','sleep','study','eat','eat']
hobbies.insert(1,'walk')
hobbies.insert(1,['walk1','walk2','walk3'])
print(hobbies)

print(hobbies.count('eat'))
print(hobbies)
hobbies.extend(['walk1','walk2','walk3'])
print(hobbies)

hobbies=['play','eat','sleep','study','eat','eat']
print(hobbies.index('eat'))


了解部分
hobbies=['play','eat','sleep','study','eat','eat']
hobbies.clear()
print(hobbies)

l=hobbies.copy()
print(l)

l=[1,2,3,4,5]
l.reverse()
print(l)

l=[100,9,-2,11,32]
l.sort(reverse=True)
print(l)

循环

msg_dic={
'apple':10,
'tesla':1000000,
'mac':3000,
'lenovo':30000,
'chicken':10,
}

index=0
while index < len(msg):
    print(msg[index])
    index+=1

不依赖索引的取值
msg_dic={
'apple':10,
'tesla':1000000,
'mac':3000,
'lenovo':30000,
'chicken':10,
}
for item in msg_dic:
    print(item,msg_dic[item])

补充
range:顾头不顾尾，默认从0开始
print(type(range(1,2)))
for i in range(10):
    print(i,type(i))

break
continue


for i in range(10):
    if i == 4:
        # break
        continue
    print(i)


for+else


for i in range(10):
    print(i)
    break
else:
    print('===>')