116 lines
7.0 KiB
Markdown
116 lines
7.0 KiB
Markdown
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---
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title: The Python Objects
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localeTitle: Python对象
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---
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> 在Python中，一切都是_对象_ 。
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_对象_表示属性的逻辑分组。属性是数据和/或功能。在Python中创建对象时，将使用_标识_ ， _类型_和_值_创建对象。
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在其他语言中， _原始数据_是没有_属性_ （属性） _值_ 。例如，在javascript `undefined` ， `null` ， `boolean` ， `string` ， `number`和`symbol` （ECMAScript 2015中的新内容）是原语。
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在Python中，没有原语。 `None` ， _布尔值_ ， _字符串_ ， _数字_甚至_函数_都是_对象，_无论它们是如何创建的。
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我们可以使用一些内置函数来演示：
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* [`id`](https://docs.python.org/3/library/functions.html#id)
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* [`type`](https://docs.python.org/3/library/functions.html#type)
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* [`dir`](https://docs.python.org/3/library/functions.html#dir)
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* [`issubclass`](https://docs.python.org/3/library/functions.html#issubclass)
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内置常量`None` ， `True`和`False`是_对象_ ：
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我们在这里测试`None`对象。
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```python
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>>> id(None)
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4550218168
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>>> type(None)
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<class 'NoneType'>
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>>> dir(None)
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[__bool__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__']
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>>> issubclass(type(None), object)
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True
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```
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接下来，让我们检查一下`True` 。
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```python
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>>> id(True)
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4550117616
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>>> type(True)
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<class 'bool'>
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>>> dir(True)
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['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']
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>>> issubclass(type(True), object)
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True
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```
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没理由遗漏`False` ！
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```python
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>>> id(False)
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4550117584
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>>> type(False)
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<class 'bool'>
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>>> dir(False)
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['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']
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>>> issubclass(type(False), object)
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True
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```
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_字符串_ ，即使通过字符串文字创建的，也是_对象_ 。
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```python
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>>> id("Hello campers!")
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4570186864
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>>> type('Hello campers!')
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<class 'str'>
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>>> dir("Hello campers!")
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['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
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>>> issubclass(type('Hello campers!'), object)
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True
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```
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与_数字_相同
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```python
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>>> id(42)
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4550495728
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>>> type(42)
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<class 'int'>
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>>> dir(42)
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['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']
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>>> issubclass(type(42), object)
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True
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```
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## 功能也是对象
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> 在Python中，函数是第一类对象。
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Python中的_函数_也是使用_标识_ ， _类型_和_值_创建的_对象_ 。它们也可以传递给其他_函数_ ：
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```python
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>>> id(dir)
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4568035688
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>>> type(dir)
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<class 'builtin_function_or_method'>
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>>> dir(dir)
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['__call__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__text_signature__']
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>>> issubclass(type(dir), object)
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True
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```
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也可以将函数绑定到名称，并使用该名称调用绑定函数：
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```python
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>>> a = dir
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>>> print(a)
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<built-in function dir>
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>>> a(a)
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['__call__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__name__', '__ne__', '__new__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__text_signature__']
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```
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资源：
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* [点击这里](https://www.jeffknupp.com/blog/2014/06/18/improve-your-python-python-classes-and-object-oriented-programming/)了解更多信息。
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