python 数据类型互相转换

int(x=0) -> integer
int(x, base=10) -> integer

In [1]: int(1.0)                                                                                      
Out[1]: 1

In [2]: int("1")                                                                                      
Out[2]: 1

In [4]: int(True)                                                                                     
Out[4]: 1

In [5]: int(False)                                                                                    
Out[5]: 0

float(x) -> floating point number

In [9]: float(1)                                  
Out[9]: 1.0

In [10]: float("1.1")                             
Out[10]: 1.1

In [11]: float(True)                              
Out[11]: 1.0

In [12]: float(False)                             
Out[12]: 0.0

complex(real[, imag]) -> complex number

In [17]: complex(1)                               
Out[17]: (1+0j)

In [18]: complex(1.0)                             
Out[18]: (1+0j)

In [19]: complex("1.0")                           
Out[19]: (1+0j)

In [20]: complex("1")                             
Out[20]: (1+0j)

In [21]: complex(True)                            
Out[21]: (1+0j)

In [22]: complex(False)                           
Out[22]: 0j

str(object='') -> str
str(bytes_or_buffer[, encoding[, errors]]) -> str

In [27]: str(1)                                  
Out[27]: '1'

In [28]: str(1.0)                                
Out[28]: '1.0'

In [29]: str(0j)                                  
Out[29]: '0j'

In [30]: str(True)                                
Out[30]: 'True'

bool(x) -> bool

In [34]: for i in ["", 0, 0.0, [], (), {}, set(), 0j, False]: 
    ...:     print(i, "is", bool(i)) 
    ...:                                          
 is False
0 is False
0.0 is False
[] is False
() is False
{} is False
set() is False
0j is False
False is False

list() -> new empty list
list(iterable) -> new list initialized from iterable's items

In [36]: list("abc")                              
Out[36]: ['a', 'b', 'c']

In [37]: list({"a", "b", "c"})                    
Out[37]: ['c', 'a', 'b']

In [38]: list(("a", "b", "c"))                    
Out[38]: ['a', 'b', 'c']

In [39]: list({"a": 1, "b":2, "c": 3})            
Out[39]: ['a', 'b', 'c']

dict(mapping) -> new dictionary initialized from a mapping object's
dict(iterable) -> new dictionary initialized as if via
dict(**kwargs) -> new dictionary initialized with the name=value pairs in the keyword argument list.

In [50]: dict([["a", 1], ["b",2]])               
Out[50]: {'a': 1, 'b': 2}

In [51]: dict((["a", 1], ["b",2]))               
Out[51]: {'a': 1, 'b': 2}

In [52]: dict((("a", 1), ("b",2)))               
Out[52]: {'a': 1, 'b': 2}

In [67]: dict(a="1",b="2")                                                                                                                                                            
Out[67]: {'a': '1', 'b': '2'}

tuple() -> empty tuple
tuple(iterable) -> tuple initialized from iterable's items

In [54]: tuple([1,2,3])                          
Out[54]: (1, 2, 3)

In [55]: tuple({1,2,3})                          
Out[55]: (1, 2, 3)

In [56]: tuple("abc")                            
Out[56]: ('a', 'b', 'c')

In [57]: tuple({"a":1,"b":2})                    
Out[57]: ('a', 'b')

set(iterable) -> new set object

In [59]: set([1,2,3])                            
Out[59]: {1, 2, 3}

In [60]: set((1,2,3))                            
Out[60]: {1, 2, 3}

In [61]: set("abc")                              
Out[61]: {'a', 'b', 'c'}

In [62]: set({"a":1, "b":2})                     
Out[63]: {'a', 'b'}