1,基础数据类型,总结补充.
int:bit_lenth()
str:
captilze() 首字母大写,其余小写.
upper() 全大写.
lower() 全小写.
find() 通过元素找索引,没有返回-1,有切片.
index() 通过元素找索引,没有回报错.有切片
swapcase() 大小写反转.
strip() 去除前后端的空格,
, ,
strip('abc') 去除前后端的a ,b,c三个元素,
ltrip ,rtrip
title 非字母隔开的部分,首字母大写
split str---> list 默认以空格(可以设定分隔符),
startswith 判断s以什么开头,返回bool值,可以切片
endswith 判断以什么结尾,返回bool值,可以切片
replace(old,new) 默认不写次数,全体换
center 以其为中心,默认填充物 空格.
count 计算元素出现的次数.
len() 测量字符串的长度.
join '' '*' '_'.... .join(interable)
isalpha() 全都是字母组成
isdigit() 全都是数字组成
isalnum() 全都是字母或者数字
'%s' %(name)
name1 = 'taibai '
'%(name)s' %{name:name1}
format
'{}{}{}'.format(name,age,hobby)
'{0}{1}{2}{1}'.format(name,age,bobby)
'{name},{age}'.format(age=12,name='太白')
int数字
str字符串
s = ' ' #只能是以至少一个空格组成的字符串(全空格)
print(s.isspace())
tuple元祖
tu = (1)
tu1 = (1,)
print(tu,type(tu))
print(tu1,type(tu1))
tu = ('alex')
tu1 = ('alex',)
print(tu,type(tu))
print(tu1,type(tu1))
tu = ([1,2,3])
tu1 = ([1,2,3],)
print(tu,type(tu))
print(tu1,type(tu1))
当元组只有一个元素组成并且没有','
则该元素是什么数据类型,整体就是什么数据类型.
tu.append('333')
print(tu)
list
l1 = [111,222,333,444,555]
for i in range(len(l1)):
# i = 0 i = 1 i = 2 i = 3
print(l1)
del l1[i]
print(l1) # [222,333,444,555] [222,444,555] [222,444]
print(l1)
l1 = [111,222,333,444,555] 将索引为奇数位的元素删除.
l1.pop(222)
l1.remove(1)
方法一:
l1 = [111,222,333,444,555]
l2 = []
for i in range(len(l1)):
if i % 2 == 0:
l2.append(l1[i])
l1 = l2
print(l1)
方法二:
l1 = [111,222,333,444,555]
for i in range(1,len(l1)):
if i <= 2 :
l1.pop(i)
print(l1)
方法二:
l1 = [111,222,333,444,555,666,777]
#
del l1[1::2]
print(l1)
l1 = [111,222,333,444,555]
for i in range(len(l1)-1,0,-1):
if i % 2 == 1:
del l1[i]
print(l1)
在循环一个列表时,如果要是删除某些或者某类元素,容易出错.
fromkeys()
dic = dict.fromkeys('abc','alex')
print(dic)
dic1 = dict.fromkeys([1,2,3],[])
print(dic1)
dic1[1].append('alex')
print(dic1)
dic = {'k1':'alex','k2':'太白','k3':'日天','name':'wusir'}
不可变的数据类型:可哈希
for i in dic:
if 'k' in i:
del dic[i]
l1 = []
for i in dic:
if 'k' in i:
l1.append(i)
print(l1)
for k in l1:
del dic[k]
print(dic)
在循环一个字典时,如果删除某些键值对,可能会报错.
数据类型之间的转化:
int <---> str
int <---> bool
str <--->.bool
split
str <------> list
join
tuple <---> list
l1 = [1,2,3]
tu = tuple(l1)
l2 = list(tu)
print(tu,l2)
dict专属类型:与list转换
dic = {'k1':'alex','k2':'太白','k3':'日天','name':'wusir'}
print(list(dic.keys()))
print(list(dic.values()))
print(list(dic.items()))
2,深浅copy.
l1 = [1,2,3,4]
l2 = l1
l1.append(5)
print(l1,l2)
对于赋值运算,就是共同指向一个内存地址.
s1 = 'alex'
s2 = s1
s1 = 'alex2'
print(s1,id(s1))
print(s2,id(s2))
copy
l1 = [1,2,3]
l2 = l1.copy()
l1.append(666)
print(l1,id(l1))
print(l2,id(l2))
l1 = [1,[22,33],2,3]
l2 = l1.copy()
l1.append(666)
print(l1,id(l1))
print(l2,id(l2))
l1 = [1,[22,33,],2,3]
l2 = l1.copy()
l1[1].append(666)
print(l1,id(l1),id(l1[1]))
print(l2,id(l2),id(l2[1]))
对于浅copy来说,第一层都是独立的内存地址,从第二层开始,都是指向同一个内存地址,一变都变.
import copy
l1 = [1,[22,33,],2,3]
l2 = copy.deepcopy(l1)
l1.append(777)
l1[1].append(666)
print(l1,id(l1),id(l1[1]))
print(l2,id(l2),id(l2[1]))
对于深copy,无论多少层,在内存中都是两个独立的内存地址.
l1 = [1,[1,2],2,3]
l2 = l1[:] # 是浅copy
l1[1].append(111)
print(l1,l2)
l2 是什么?