深入理解python

python

1 python自身的威力

1.1 使用type、str、dir、其他内置函数

//type函数:返回任意对象的数据类型.比如:整型、字符串、列表、字典、元组、函数、类、模块,甚至类型对象都可以作为参数被  type 函数接受。

>>> type(123)

<class 'int'>

>>> type("11")

<class 'str'>

>>> li=[]

>>> type(li)

<class 'list'>

//str函数:str将数据强制转换成字符串,每种数据类型都可以转换为字符串。

>>> type(str(1))

<class 'str'>

>>> li=[]

>>> type(str(li))

<class 'str'>

//dir函数:返回任意对象的属性和方法列表,包括模块对象、函数对象、字符串对象、列表对象、字典对象

>>> dir(__builtins__)

['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning', 'ChildProcessError',
'ConnectionAbortedError', 'ConnectionError', 'ConnectionRefusedError', 'ConnectionResetError', 'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError',
'Exception', 'False', 'FileExistsError', 'FileNotFoundError', 'FloatingPointError', 'FutureWarning', 'GeneratorExit', 'IOError', 'ImportError', 'ImportWarning',
'IndentationError', 'IndexError', 'InterruptedError', 'IsADirectoryError', 'KeyError', 'KeyboardInterrupt', 'LookupError', 'MemoryError', 'ModuleNotFoundError',
'NameError', 'None', 'NotADirectoryError', 'NotImplemented', 'NotImplementedError', 'OSError', 'OverflowError', 'PendingDeprecationWarning', 'PermissionError',
'ProcessLookupError', 'RecursionError', 'ReferenceError', 'ResourceWarning', 'RuntimeError', 'RuntimeWarning', 'StopAsyncIteration', 'StopIteration', 'SyntaxError',
'SyntaxWarning', 'SystemError', 'SystemExit', 'TabError', 'TimeoutError', 'True', 'TypeError', 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError',
'UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning', 'ValueError', 'Warning', 'WindowsError', 'ZeroDivisionError', '__build_class__', '__debug__',
'__doc__', '__import__', '__loader__', '__name__', '__package__', '__spec__', 'abs', 'all', 'any', 'ascii', 'bin', 'bool', 'breakpoint', 'bytearray', 'bytes',
'callable', 'chr', 'classmethod', 'compile', 'complex', 'copyright', 'credits', 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'exec', 'exit', 'filter',
'float', 'format', 'frozenset', 'getattr', 'globals', 'hasattr', 'hash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass', 'iter', 'len', 'license',
'list', 'locals', 'map', 'max', 'memoryview', 'min', 'next', 'object', 'oct', 'open', 'ord', 'pow', 'print', 'property', 'quit', 'range', 'repr', 'reversed', 'round',
'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'vars', 'zip']

//help()函数:

>>> help()

To get a list of available modules, keywords, symbols, or topics, type

"modules", "keywords", "symbols", or "topics". Each module also comes

with a one-line summary of what it does; to list the modules whose name

or summary contain a given string such as "spam", type "modules spam".

help> input

Help on built-in function input in module builtins:

input(prompt=None, /)

Read a string from standard input. The trailing newline is stripped.

The prompt string, if given, is printed to standard output without a

trailing newline before reading input.

If the user hits EOF (*nix: Ctrl-D, Windows: Ctrl-Z+Return), raise EOFError.

On *nix systems, readline is used if available.

help>

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