python基础之数据类型转换

方法转换：str -->list str.split()    list -->str ''.join(list)
强制转换：str -->list  list(str)     str -->tuple  tuple(str)  str -->set  set(str)
          list -->tuple  tuple(list)  list -->set  set(list)
          tuple -->list  list(tuple)  tuple -->set set(tuple)
          set -->list  list(set)      set -->tuple  tuple(set)
          str,tuple,list,dict,set -->bool  bool(obj)

1,str --> list  split
ey:

str1 = 'a b c d'
list1 = str1.split()
print(list1)

result:['a', 'b', 'c', 'd']
ey:

str1 = 'a,b,c,d'
list1 = str1.split(',')
print(list1)

result:['a', 'b', 'c', 'd']
ey:

str1 = 'abcd'
list1 = str1.split('c')
print(list1)

result:['ab', 'd']
2，list --> str  join
ey:

list2 = ['','','','dd']
str2 = '*'.join(list2)
print(str2)

result:1*2*3*dd
3,强制转换
str --> list
ey:

str1 = 'abcd'
list1 = list(str1)
print(list1)

result:['a', 'b', 'c', 'd']
4,str -->tuple

s1 = '123wwrw'
print(tuple(s1))

result:('1', '2', '3', 'w', 'w', 'r', 'w')
5,str -->set

s1 = '123wwrw'
print(set(s1))

result:{'1', 'w', 'r', '3', '2'}
6,空的str list tuple dict set 转换为bool 为false ，非空为true
7,list --> set  达到去重效果,list内容需为不可变数据类型

l1 = [1,2,31,1,2]
set1 = set(l1)
print(set1)

result:{1, 2, 31}
ey:

l1 = [1,2,31,1,2,[12,33]]
tu2 = set(l1)
print(tu2)

result:TypeError: unhashable type: 'list'
8，set -->list

set1 = set({1,2,3})
l1 = list(set1)
print(l1)

result:[1, 2, 3]
9,list -->tuple

l1 = [1,2,31,1,2]
tu1 = tuple(l1)
print(tu1)

result:(1, 2, 31, 1, 2)
10,tuple -->list

tu1 = (1,2,3)
l2 = list(tu1)
print(l2)

result:[1, 2, 3]
11, tuple -->set

tu1 = (1,2,3)
set2 = set(tu1)
print(set2)

result:{1, 2, 3}
12,set -->tuple

set1 = set({1,2,3})
tu1 = tuple(set1)
print(tu1)

result:(1, 2, 3)