Goal: Learn about built-in functions in python.

# import __builtin__ module to be able to get help on it
import __builtin__

# to quickly check what's inside:
dir(__builtin__)
['ArithmeticError', 'AssertionError', 'AttributeError', 
'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError'
'Exception', 'False', 'FloatingPointError', 'FutureWarning', 
'IOError', 'ImportError', 'IndentationError', 'IndexError', 
'KeyError', 'KeyboardInterrupt', 'LookupError', 'MemoryError', 
'NameError', 'None', 'NotImplemented', 'NotImplementedError', 
'OSError', 'OverflowError', 'OverflowWarning', 
'PendingDeprecationWarning', 'ReferenceError', 'RuntimeError', 
'RuntimeWarning', 'StandardError', 'StopIteration', 
'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit', 
'TabError', 'True', 'TypeError', 'UnboundLocalError', 
'UnicodeDecodeError', 'UnicodeEncodeError', 'UnicodeError', 
'UnicodeTranslateError', 'UserWarning', 'ValueError', 'Warning',
'ZeroDivisionError', '_', '__debug__', '__doc__', '__import__',
'__name__', 'abs', 'apply', 'basestring', 'bool', 'buffer', 
'callable', 'chr', 'classmethod', 'cmp', 'coerce', 'compile', 
'complex', 'copyright', 'credits', 'delattr', 'dict', 'dir', 
'divmod', 'enumerate', 'eval', 'execfile', 'exit', 'file', 
'filter', 'float', 'frozenset', 'getattr', 'globals', 'hasattr',
'hash', 'help', 'hex', 'id', 'input', 'int', 'intern', 
'isinstance', 'issubclass', 'iter', 'len', 'license', 'list', 
'locals', 'long', 'map', 'max', 'min', 'object', 'oct', 'open', 
'ord', 'pow', 'property', 'quit', 'range', 'raw_input', 'reduce'
'reload', 'repr', 'reversed', 'round', 'set', 'setattr', 
'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super', 
'tuple', 'type', 'unichr', 'unicode', 'vars', 'xrange', 'zip']
 

# check also the help() function
help(__builtin__)
Help on built-in module __builtin__:

NAME
    __builtin__ - Built-in functions, exceptions, and other objects.

FILE
    (built-in)

DESCRIPTION
    Noteworthy: None is the `nil' object; Ellipsis represents `...' in slices.

CLASSES
    object
        basestring
            str
            unicode
        buffer
        classmethod
        complex
        dict

# or more specifilcally you can inquire about 
# the intrinsic 'file' object
help(__builtin__.file)
Help on class file in module __builtin__:

class file(object)
 |  file(name[, mode[, buffering] ]) -> file object
 |
 |  Open a file.  The mode can be 'r', 'w' or 'a' for reading (default),
 |  writing or appending.  The file will be created if it doesn't exist
 |  when opened for writing or appending; it will be truncated when
 |  opened for writing.  Add a 'b' to the mode for binary files.
 |  Add a '+' to the mode to allow simultaneous reading and writing.
 |  If the buffering argument is given, 0 means unbuffered, 1 means line
 |  buffered, and larger numbers specify the buffer size.
 |  Add a 'U' to mode to open the file for input with universal newline
 |  support.  Any line ending in the input file will be seen as a '\n'
 |  in Python.  Also, a file so opened gains the attribute 'newlines';
 |  the value for this attribute is one of None (no newline read yet),
 |  '\r', '\n', '\r\n' or a tuple containing all the newline types seen.
 |
 |  'U' cannot be combined with 'w' or '+' mode.
 |
 |  Note:  open() is an alias for file().
 |
 |  Methods defined here:
 |
 |  __delattr__(...)
 |      x.__delattr__('name') <==> del x.name
 |
 |  __getattribute__(...)
 |      x.__getattribute__('name') <==> x.name

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