python基础4

一、for循环

l=['a','b','c']
print(len(l))
i=0
while i<len(l):
    print(l[i])
    i+=1

l=['a''b''c']
for itme in l:
    print(itme)

dic={'x':111,'y':222,'z':333}
for k in dic:
    print(k,dic[k])

while循环VSfor循环
1、while循环称之为条件循环，循环次数取决于何时为False
  for循环称之为。。。，循环次数取决于数据包含的元素个数
2、for循环专门用来取值，在循环取值方面比while还要强大，但凡遇到取值就应该用到for循环。

l=['a','b','c']
for i in range(3):
    print(i,l[i])

for+break
names=['egon','kevin','alex','hulaoshi']
for name in names:
    if name=='alex':break
    print(name)

for+continue
names=['egon','kevin','alex','hulaoshi']
for name in names:
    if name=='alex':continue
    print(name)

for+else
names=['egon','kevin','alex','hulaoshi']
for name in names:
    if name=='alex':break
    print(name)
else:
    print('>>>>:')

for循环嵌套

for i in range(3):
    for j in range(2):
        print(i,j)
        外层循环第一次：i=0
    内层循环
        0，0
        0，1

外层循环第二次：i=1
    内层循环
        1，0
        1，1
外层循环第三次: i=2
    内层循环
        2,0
        2,1
print(' ',end='
')#自动换行
print('bbbbb',end='') #不换行

二、数字类型
1、整形int

======================================基本使用======================================
# 1、用途：记录年龄、等级、号码等

# 2、定义方式
age=10 # age=int(10)

 类型转换
 print(int(3.1))
rea=float('111.1')
print(rea,type(rea))

进制转换（了解）
十进制转成。。。进制
print（bin(13))转二进制
print（oct（13））转8进制
print（hex（13）转16进制

#3、常用操作+内置的方法

======================================该类型总结====================================
 存一个值

 不可变
x=10
print(id(x))
x=11
print(id(x))

2、浮点型float

======================================基本使用======================================
# 1、用途：记录年龄、等级、号码等

# 2、定义方式
age=10 # age=int(10)

 类型转换
 print(int(3.1))
rea=float('111.1')
print(rea,type(rea))

进制转换（了解）
十进制转成。。。进制
print（bin(13))转二进制
print（oct（13））转8进制
print（hex（13）转16进制

#3、常用操作+内置的方法

======================================该类型总结====================================
 存一个值

 不可变
x=10
print(id(x))
x=11
print(id(x))

三、字符串类型.

字符串类型str:
======================================基本使用======================================
 1、用途：记录描述性值的状态，比如名字、性别等

 2、定义方式
 msg='hello word'# msg=str('hello word')
 类型转换：可以将任意类型转成字符串类型
 res1=str(10)
res2=str(10.3)
res3=str([1,2,3])
res4=str({'x':1}) #res4="{'x':1}"

print(type(res1))
print(type(res2))
print(type(res3))
print(type(res4))
3、常用操作+内置的方法
优先掌握的操作：（*****）

#1、按索引取值(正向取+反向取) ：只能取

msg='hell word'
print(type(msg[0]))
print(msg[-1])

#2、切片(顾头不顾尾，步长)

msg='hello world'
 print(msg[0]+msg[1]+msg[2])
 print(msg[0:5])
 print(msg[0:5:2]) #0 2 4
 print(msg[0:]) #
 print(msg[:])
 print(msg[-1:-5:-1]) #-1 -2 -3 -4
 print(msg[::-1]) #-1 -2 -3 -4

#3、长度len：统计的是字符的个数

msg='h你d'
print(len(msg))
msg='h你d'
print(len(msg))

#4、成员运算in和not in：判断一个子字符串是否存在与一个大字符串中

msg='hello world'
print('ho' in msg)
print('ho' not in msg)

#5、移除空白strip:移除字符串左右两边的某些字符

msg='      hello      '

print(msg.strip(' '))
print(msg.strip())
print(msg)

name=input('name>>>: ').strip() #name='egon'
pwd=input('password>>>: ').strip()

if name == 'egon' and pwd == '123':
    print('login successfull')
else:
    print('username or password error')

msg='***h**ello**********'
print(msg.strip('*'))

msg='*-=+h/ello*(_+__'
print(msg.strip('*-=+/(_'))

6、切分split: 把有规律的字符串切成列表从而方便取值

info='egon:18:180:160'
res=info.split(':'1)
print(res)
print(res(1))
info='egon:18:180:150'
res=info.split(':')
print(res)


s1=res[0]+':'+res[1]+':'+res[2]+':'+res[3]
s1=''
for item in res:
    s1+=item
print(s1)


s1=':'.join(res)
print(s1)

':'.join([1,2,3,4,5])

#7、循环

for i in 'hello':
    print(i)

需要掌握的知识（*****）
#1、strip,lstrip,rstrip
msg='*****hello word*****'
print(msg.strip('*'))#去左右两侧
print(msg.lstrip('*'))#去左侧
print(msg.rstrip('*'))#去右侧
#2、lower,upper
 msg='AaBbCc123123123'
 print(msg.lower())#转小写
 print(msg.upper())#转大写
#3、startswith,endswith
msg='alex is dsb'
print(msg.startswith('alex'))#是否在开头
print(msg.endswith('sb'))#是否在结尾
#4、format的三种玩法
msg='my name is %s my age is %s' %('egon',18)
print(msg)

msg='my name is {name} my age is {age}'.format(age=18,name='egon')#格式化输出
了解
msg='my name is {} my age is {}'.format(18,'egon')
msg='my name is {0}{0} my age is {1}{1}{1}'.format(18,'egon')#多次输出
print(msg)
#5、split,rsplit
cmd='get|a.txt|33333'
print(cmd.split('|',1))
print(cmd.rsplit('|',1))
#6、replace
msg='kevin is sb kevin kevin'
print(msg.replace('kevin','sb',2))
#7、isdigit #当字符串内为纯数字时结果为True
res='11111'
print(res.isdigit())
int(res)
age_of_bk=18
inp_age=input('your age: ').strip()
if inp_age.isdigit():
    inp_age=int(inp_age) #int('asdfasdfadfasdf')
    if inp_age > 18:
        print('too big')
    elif inp_age < 18:
        print('to small')
    else:
        print('you got it')
else:
    print('必须输入纯数字')

　　

了解（**）
#1、find,rfind,index,rindex,count
print('xxxkevin is sb kevin'.find('kevin'))
print('xxxkevin is sb kevin'.index('kevin'))
print('xxxkevin is sb kevin'.rfind('kevin'))
print('xxxkevin is sb kevin'.rindex('kevin'))


res='xxxkevin is sb kevin'.find('kevasdfsadfin')
print(res)

res='xxxkevin is sb kevin'.index('kevasdfsadfin')



print('kevin is kevin is kevin is sb'.count('kevin'))

#2、center,ljust,rjust,zfill
print('egon'.center(50,'*'))
print('egon'.ljust(50,'*'))
print('egon'.rjust(50,'*'))
print('egon'.zfill(50))

#3、captalize,swapcase,title
print('my name is kevin'.capitalize())
print('AaBbCc'.swapcase())
print('my name is kevin'.title())

#4、is其他
name='egon123'
print(name.isalnum()) #字符串由字母或数字组成
print(name.isalpha()) #字符串只由字母组成

print(name.islower())
print(name.isupper())
name='    '
print(name.isspace())
msg='I Am Egon'
print(msg.istitle())