Exploring Python

Whether you use IDLE or the Interactive Shell, there are some useful functions to explore Python.

>>> x = 4.2

type()

With type(), you can display the object type, for example:

>>> type(x)
<class 'float'>

help()

help() has two different modes. When you type help(), you call the help system, which you can use to get information about modules, keywords, and other topics. When you are in the help system, you will see a prompt with help>. You can now enter a module name, for example float, to search the Python documentation for that type.

help() is part of the pydoc library, which provides access to the documentation built into Python libraries. Since every Python installation comes with full documentation, you have all the documentation at your fingertips even offline.

Alternatively, you can use help() more specifically by passing a type or variable name as a parameter, for example:

>>> help(x)
Help on float object:

class float(object)
 |  float(x=0, /)
 |
 |  Convert a string or number to a floating point number, if possible.
 |
 |  Methods defined here:
 |
 |  __abs__(self, /)
 |      abs(self)
...
|  is_integer(self, /)
|      Return True if the float is an integer.
...

For example, you will learn that x is of type float and has a function

is_integer() that you can use with dot notation:

>>> x.is_integer()
False

id()

id() specifies the identification number of an object, for example:

>>> id(x)
4304262800

dir()

dir() is another useful function to find out which methods and data are available locally or for a specific object:

>>> dir()
['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'x']

For example, we can use dir(__builtins__) to display a list of what is already available in the Python standard library:

>>> dir(__builtins__)
['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'BaseExceptionGroup', 'BlockingIOError', 'BrokenPipeError', 'BufferError', 'BytesWarning', 'ChildProcessError', 'ConnectionAbortedError', 'ConnectionError', 'ConnectionRefusedError', 'ConnectionResetError', 'DeprecationWarning', 'EOFError', 'Ellipsis', 'EncodingWarning', 'EnvironmentError', 'Exception', 'ExceptionGroup', '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', 'PythonFinalizationError', 'RecursionError', 'ReferenceError', 'ResourceWarning', 'RuntimeError', 'RuntimeWarning', 'StopAsyncIteration', 'StopIteration', 'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit', 'TabError', 'TimeoutError', 'True', 'TypeError', 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError', 'UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning', 'ValueError', 'Warning', 'ZeroDivisionError', '_', '_IncompleteInputError', '__build_class__', '__debug__', '__doc__', '__import__', '__loader__', '__name__', '__package__', '__spec__', 'abs', 'aiter', 'all', 'anext', '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']