Python magic method (9):__ dir__ (self) method

Python There are some magical ways to do it , They are always surrounded by double underscores , They are object-oriented Of Python Everything . They are special ways to add magic to your classes , If your object implements （ heavy load ） A magic method , Then this method will be automatically used in special cases Python The call .

function

Definition object is dir() The behavior of a function call .

Parameters

self Represents the object itself .

Return value

An iteratable object .

Example ：

class MyTest(object):
def __init__(self):
self.name = ' Jane '
self.age = 18
def __dir__(self) -> 'Iterable[str]':
dic = self.__dict__.copy()
if 'name' in dic:
dic.pop('name')
return dic
sample = MyTest()
print(dir(sample))

class CLanguage:
def __init__(self, ):
self.name = "C Chinese language network "
self.add = "http://c.biancheng.net"
def say(self):
pass
clangs = CLanguage()
print(dir(clangs))

adopt dir() function , Not only output the newly added attribute names and methods in this class （ Last 3 individual ）, Also output from the parent class （ Here for object class ） Inherited property name and method name .

dir() Internal implementation of function , It's actually calling the parameter object __dir__() Based on the method , Sort the property name and method name returned by this method .
therefore , Besides using dir() function , You can call the __dir__() Method ：

class CLanguage:
def __init__(self, ):
self.name = "C Chinese language network "
self.add = "http://c.biancheng.net"
def say(self):
pass
clangs = CLanguage()
print(clangs.__dir__())

Use __dir__() Methods and dir() The output data of the function is the same , Only in different order .