文章目录

    • refs
    • python命令行文档
      • python --help
    • python help函数
      • 进入帮助系统(简练的python文档系统)
      • 查阅内置模块(函数/异常/对象)
      • 内置类型
      • 区分大小写
      • 查看可用的帮助话题
      • 可用的符号
      • 可用模块
      • 查看具体对象
      • 查看指定对象函数的帮助
    • eval
    • repr
  • 内置函数源代码查看
    • 某些内置函数无法直接通过IDE查看

refs

  • str() vs repr() in Python - GeeksforGeeks

python命令行文档

  • 3.11.1 Documentation (python.org)

python --help

  • python --help

  • usage: D:\Program Files\Python310\python.exe [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-b     : issue warnings about str(bytes_instance), str(bytearray_instance)and comparing bytes/bytearray with str. (-bb: issue errors)
-B     : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x
-c cmd : program passed in as string (terminates option list)
-d     : turn on parser debugging output (for experts only, only works ondebug builds); also PYTHONDEBUG=x
-E     : ignore PYTHON* environment variables (such as PYTHONPATH)
-h     : print this help message and exit (also -? or --help)
-i     : inspect interactively after running script; forces a prompt evenif stdin does not appear to be a terminal; also PYTHONINSPECT=x
-I     : isolate Python from the user's environment (implies -E and -s)
-m mod : run library module as a script (terminates option list)
-O     : remove assert and __debug__-dependent statements; add .opt-1 before.pyc extension; also PYTHONOPTIMIZE=x
-OO    : do -O changes and also discard docstrings; add .opt-2 before.pyc extension
-q     : don't print version and copyright messages on interactive startup
-s     : don't add user site directory to sys.path; also PYTHONNOUSERSITE
-S     : don't imply 'import site' on initialization
-u     : force the stdout and stderr streams to be unbuffered;this option has no effect on stdin; also PYTHONUNBUFFERED=x
-v     : verbose (trace import statements); also PYTHONVERBOSE=xcan be supplied multiple times to increase verbosity
-V     : print the Python version number and exit (also --version)when given twice, print more information about the build
-W arg : warning control; arg is action:message:category:module:linenoalso PYTHONWARNINGS=arg
-x     : skip first line of source, allowing use of non-Unix forms of #!cmd
-X opt : set implementation-specific option. The following options are available:-X faulthandler: enable faulthandler-X showrefcount: output the total reference count and number of usedmemory blocks when the program finishes or after each statement in theinteractive interpreter. This only works on debug builds-X tracemalloc: start tracing Python memory allocations using thetracemalloc module. By default, only the most recent frame is stored in atraceback of a trace. Use -X tracemalloc=NFRAME to start tracing with atraceback limit of NFRAME frames-X importtime: show how long each import takes. It shows module name,cumulative time (including nested imports) and self time (excludingnested imports). Note that its output may be broken in multi-threadedapplication. Typical usage is python3 -X importtime -c 'import asyncio'-X dev: enable CPython's "development mode", introducing additional runtimechecks which are too expensive to be enabled by default. Effect of thedeveloper mode:* Add default warning filter, as -W default* Install debug hooks on memory allocators: see the PyMem_SetupDebugHooks()C function* Enable the faulthandler module to dump the Python traceback on a crash* Enable asyncio debug mode* Set the dev_mode attribute of sys.flags to True* io.IOBase destructor logs close() exceptions-X utf8: enable UTF-8 mode for operating system interfaces, overriding the defaultlocale-aware mode. -X utf8=0 explicitly disables UTF-8 mode (even when it wouldotherwise activate automatically)-X pycache_prefix=PATH: enable writing .pyc files to a parallel tree rooted at thegiven directory instead of to the code tree-X warn_default_encoding: enable opt-in EncodingWarning for 'encoding=None'
--check-hash-based-pycs always|default|never:control how Python invalidates hash-based .pyc files
file   : program read from script file
-      : program read from stdin (default; interactive mode if a tty)
arg ...: arguments passed to program in sys.argv[1:]Other environment variables:
PYTHONSTARTUP: file executed on interactive startup (no default)
PYTHONPATH   : ';'-separated list of directories prefixed to thedefault module search path.  The result is sys.path.
PYTHONHOME   : alternate <prefix> directory (or <prefix>;<exec_prefix>).The default module search path uses <prefix>\python{major}{minor}.
PYTHONPLATLIBDIR : override sys.platlibdir.
PYTHONCASEOK : ignore case in 'import' statements (Windows).
PYTHONUTF8: if set to 1, enable the UTF-8 mode.
PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.
PYTHONFAULTHANDLER: dump the Python traceback on fatal errors.
PYTHONHASHSEED: if this variable is set to 'random', a random value is usedto seed the hashes of str and bytes objects.  It can also be set to aninteger in the range [0,4294967295] to get hash values with apredictable seed.
PYTHONMALLOC: set the Python memory allocators and/or install debug hookson Python memory allocators. Use PYTHONMALLOC=debug to install debughooks.
PYTHONCOERCECLOCALE: if this variable is set to 0, it disables the localecoercion behavior. Use PYTHONCOERCECLOCALE=warn to request display oflocale coercion and locale compatibility warnings on stderr.
PYTHONBREAKPOINT: if this variable is set to 0, it disables the defaultdebugger. It can be set to the callable of your debugger of choice.
PYTHONDEVMODE: enable the development mode.
PYTHONPYCACHEPREFIX: root directory for bytecode cache (pyc) files.
PYTHONWARNDEFAULTENCODING: enable opt-in EncodingWarning for 'encoding=None'.

python help函数

help(request)

  • Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.

  • Note that if a slash(/) appears in the parameter list of a function when invoking help(), it means that the parameters prior to the slash are positional-only. For more info, see the FAQ entry on positional-only parameters.

  • This function is added to the built-in namespace by the site module.

进入帮助系统(简练的python文档系统)

  • >>> help()Welcome to Python 3.9's help utility!If this is your first time using Python, you should definitely check out
the tutorial on the Internet at https://docs.python.org/3.9/tutorial/.Enter the name of any module, keyword, or topic to get help on writing
Python programs and using Python modules.  To quit this help utility and
return to the interpreter, just type "quit".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>

  • 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”.

查阅内置模块(函数/异常/对象)

  • help("builtins")

  • 通常传入字符串给help()函数更有可能查询成功

  • 例如help(builtins)会报错,但是help("builtins")则可以正确工作

  • 或者进入帮助交互系统

    help>  builtins
Help on built-in module builtins:NAMEbuiltins - Built-in functions, exceptions, and other objects.DESCRIPTIONNoteworthy: None is the `nil' object; Ellipsis represents `...' in slices.CLASSESobjectBaseExceptionExceptionArithmeticErrorFloatingPointErrorOverflowErrorZeroDivisionErrorAssertionErrorAttributeErrorBufferErrorEOFErrorImportErrorModuleNotFoundErrorLookupErrorIndexErrorKeyErrorMemoryErrorNameErrorUnboundLocalErrorOSErrorBlockingIOErrorChildProcessErrorConnectionErrorBrokenPipeErrorConnectionAbortedErrorConnectionRefusedErrorConnectionResetErrorFileExistsErrorFileNotFoundErrorInterruptedErrorIsADirectoryErrorNotADirectoryErrorPermissionErrorProcessLookupErrorTimeoutErrorReferenceErrorRuntimeErrorNotImplementedError
.....sorted(iterable, /, *, key=None, reverse=False)Return a new list containing all items from the iterable in ascending order.A custom key function can be supplied to customize the sort order, and thereverse flag can be set to request the result in descending order.sum(iterable, /, start=0)Return the sum of a 'start' value (default: 0) plus an iterable of numbersWhen the iterable is empty, return the start value.This function is intended specifically for use with numeric values and mayreject non-numeric types.vars(...)vars([object]) -> dictionaryWithout arguments, equivalent to locals().With an argument, equivalent to object.__dict__.DATAEllipsis = EllipsisFalse = FalseNone = NoneNotImplemented = NotImplementedTrue = True__debug__ = Truecopyright = Copyright (c) 2001-2021 Python Software Foundati...ematisc...credits =     Thanks to CWI, CNRI, BeOpen.com, Zope Corpor...opment.  ...exit = Use exit() or Ctrl-Z plus Return to exithelp = Type help() for interactive help, or help(object) for help abou...license = See https://www.python.org/psf/license/quit = Use quit() or Ctrl-Z plus Return to exitFILE(built-in)

内置类型

  • help> TYPES
The standard type hierarchy
***************************Below is a list of the types that are built into Python.
...
...Python distinguishes between integers, floating point numbers, andcomplex numbers:"numbers.Integral"These represent elements from the mathematical set of integers(positive and negative).There are two types of integers:Integers ("int")These represent numbers in an unlimited range, subject toavailable (virtual) memory only.  For the purpose of shiftand mask operations, a binary representation is assumed, andnegative numbers are represented in a variant of 2Æscomplement which gives the illusion of an infinite string ofsign bits extending to the left.Booleans ("bool")These represent the truth values False and True.  The twoobjects representing the values "False" and "True" are theonly Boolean objects. The Boolean type is a subtype of theinteger type, and Boolean values behave like the values 0 and1, respectively, in almost all contexts, the exception beingthat when converted to a string, the strings ""False"" or""True"" are returned, respectively.The rules for integer representation are intended to give themost meaningful interpretation of shift and mask operationsinvolving negative integers."numbers.Real" ("float")These represent machine-level double precision floating pointnumbers. You are at the mercy of the underlying machinearchitecture (and C or Java implementation) for the acceptedrange and handling of overflow. Python does not support single-precision floating point numbers; the savings in processor andmemory usage that are usually the reason for using these aredwarfed by the overhead of using objects in Python, so there isno reason to complicate the language with two kinds of floatingpoint numbers."numbers.Complex" ("complex")These represent complex numbers as a pair of machine-leveldouble precision floating point numbers.  The same caveats applyas for floating point numbers. The real and imaginary parts of acomplex number "z" can be retrieved through the read-onlyattributes "z.real" and "z.imag".
....

区分大小写

  • 例如

    • help> types
#不同于
help> TYPES

      • help> typesHelp on module types:NAMEtypes - Define names for built-in types that aren't directly accessible as a builtin.MODULE REFERENCEhttps://docs.python.org/3.10/library/types.htmlThe following documentation is automatically generated from the Pythonsource files.  It may be incomplete, incorrect or include features thatare considered implementation detail and may vary between Pythonimplementations.  When in doubt, consult the module reference at thelocation listed above.CLASSESbuiltins.objectbuiltins.NoneTypebuiltins.NotImplementedType
      • help> TYPES
The standard type hierarchy
***************************Below is a list of the types that are built into Python.
...
...

查看可用的帮助话题

  • help> topicsHere is a list of available topics.  Enter any topic name to get more help.ASSERTION           DELETION            LOOPING             SHIFTING
ASSIGNMENT          DICTIONARIES        MAPPINGMETHODS      SLICINGS
ATTRIBUTEMETHODS    DICTIONARYLITERALS  MAPPINGS            SPECIALATTRIBUTES
ATTRIBUTES          DYNAMICFEATURES     METHODS             SPECIALIDENTIFIERS
AUGMENTEDASSIGNMENT ELLIPSIS            MODULES             SPECIALMETHODS
BASICMETHODS        EXCEPTIONS          NAMESPACES          STRINGMETHODS
BINARY              EXECUTION           NONE                STRINGS
BITWISE             EXPRESSIONS         NUMBERMETHODS       SUBSCRIPTS
BOOLEAN             FLOAT               NUMBERS             TRACEBACKS
CALLABLEMETHODS     FORMATTING          OBJECTS             TRUTHVALUE
CALLS               FRAMEOBJECTS        OPERATORS           TUPLELITERALS
CLASSES             FRAMES              PACKAGES            TUPLES
CODEOBJECTS         FUNCTIONS           POWER               TYPEOBJECTS
COMPARISON          IDENTIFIERS         PRECEDENCE          TYPES
COMPLEX             IMPORTING           PRIVATENAMES        UNARY
CONDITIONAL         INTEGER             RETURNING           UNICODE
CONTEXTMANAGERS     LISTLITERALS        SCOPING
CONVERSIONS         LISTS               SEQUENCEMETHODS
DEBUGGING           LITERALS            SEQUENCES

可用的符号

  • help> symbolsHere is a list of the punctuation symbols which Python assigns special meaning
to. Enter any symbol to get more help.!=                  +                   <=                  __
"                   +=                  <>                  `
"""                 ,                   ==                  b"
%                   -                   >                   b'
%=                  -=                  >=                  f"
&                   .                   >>                  f'
&=                  ...                 >>=                 j
'                   /                   @                   r"
'''                 //                  J                   r'
(                   //=                 [                   u"
)                   /=                  \                   u'
*                   :                   ]                   |
**                  <                   ^                   |=
**=                 <<                  ^=                  ~
*=                  <<=                 _

  • help> FUNCTIONS
Functions
*********Function objects are created by function definitions.  The only
operation on a function object is to call it: "func(argument-list)".There are really two flavors of function objects: built-in functions
and user-defined functions.  Both support the same operation (to call
the function), but the implementation is different, hence the
different object types.See Function definitions for more information.Related help topics: def, TYPES

可用模块

  • help> modulesPlease wait a moment while I gather a list of all available modules...IPython             brotli              matplotlib_inline   struct
OpenSSL             bs4                 menuinst            subprocess
__future__          builtins            mimetypes           sunau
_abc                bz2                 mistune             symbol
_aix_support        cProfile            mmap                symtable
_argon2_cffi_bindings calendar            mmapfile            sys
_ast                catalan             mmsystem            sysconfig
_asyncio            certifi             modulefinder        tabnanny
_bisect             cffi                more_itertools      tarfile
.....

查看具体对象

  • >>> help(str)
Help on class str in module builtins:class str(object)|  str(object='') -> str|  str(bytes_or_buffer[, encoding[, errors]]) -> str||  Create a new string object from the given object. If encoding or|  errors is specified, then the object must expose a data buffer|  that will be decoded using the given encoding and error handler.|  Otherwise, returns the result of object.__str__() (if defined)|  or repr(object).|  encoding defaults to sys.getdefaultencoding().|  errors defaults to 'strict'.||  Methods defined here:||  __add__(self, value, /)|      Return self+value.||  __contains__(self, key, /)|      Return key in self.|

查看指定对象函数的帮助

  • 例如,字符串类型:str的startswith函数

  • help> str.startswith
Help on method_descriptor in str:str.startswith = startswith(...)S.startswith(prefix[, start[, end]]) -> boolReturn True if S starts with the specified prefix, False otherwise.With optional start, test S beginning at that position.With optional end, stop comparing S at that position.prefix can also be a tuple of strings to try.

eval

  • eval(expression, globals=None, locals=None)

  • The arguments are a string and optional globals and locals.

    • If provided, globals must be a dictionary.

    • If provided, locals can be any mapping object.

    • The expression argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the globals and locals dictionaries as global and local namespace.

      • If the globals dictionary is present and does not contain a value for the key __builtins__, a reference to the dictionary of the built-in module builtins is inserted under that key before expression is parsed.
      • That way you can control what builtins are available to the executed code by inserting your own __builtins__ dictionary into globals before passing it to eval().
      • If the locals dictionary is omitted it defaults to the globals dictionary. If both dictionaries are omitted, the expression is executed with the globals and locals in the environment where eval() is called. Note, eval() does not have access to the nested scopes (non-locals) in the enclosing environment.

  • The return value is the result of the evaluated expression. Syntax errors are reported as exceptions. Example:

  • >>> x = 1
>>> eval('x+1')
2

  • This function can also be used to execute arbitrary code objects (such as those created by compile()). In this case, pass a code object instead of a string.

  • If the code object has been compiled with 'exec' as the mode argument, eval()'s return value will be None.

  • Hints: dynamic execution of statements is supported by the exec() function. The globals() and locals() functions return the current global and local dictionary, respectively, which may be useful to pass around for use by eval() or exec().

  • If the given source is a string, then leading and trailing spaces and tabs are stripped.

  • See ast.literal_eval() for a function that can safely evaluate strings with expressions containing only literals.

  • Raises an auditing event exec with the code object as the argument. Code compilation events may also be raised.

repr