Learning Python

Built-in Functions

The dir function is a built-in function: it lives in the built-in namespace. Applying the LGB rule means that the function is always available, and that no import statement is needed to access it.^[54] You’ve already encountered many of the built-in functions, such as len, open, type, list, map, range, reload. You can find them listed with the standard exceptions in the _ _builtins__ namespace:

>>> dir(__builtins__)
['ArithmeticError', 'AssertionError', 'AttributeError', 'EOFError', 
'Ellipsis','Exception', 'FloatingPointError', 'IOError', 'ImportError', 
'IndexError','KeyError', 'KeyboardInterrupt', 'LookupError', 'MemoryError', 
'NameError','None', 'OverflowError', 'RuntimeError', 'StandardError', 
'SyntaxError','SystemError', 'SystemExit', 'TypeError', 'ValueError', 
'ZeroDivisionError','__debug__', '__doc__', '__import__', '__name__', 'abs', 
'apply', 'callable','chr', 'cmp', 'coerce', 'compile', 'complex', 'delattr', 
'dir', 'divmod', 'eval','execfile', 'filter', 'float', 'getattr', 'globals', 
'hasattr', 'hash', 'hex','id', 'input', 'int', 'intern', 'isinstance', 
'issubclass', 'len', 'list','locals', 'long', 'map', 'max', 'min', 'oct', 
'open', 'ord', 'pow', 'range', 'raw_input', 'reduce', 'reload', 'repr', 
'round', 'setattr', 'slice', 'str','tuple', 'type', 'vars', 'xrange']

Conversions, Numbers, and Comparisons

A few functions are used for converting between object types. We’ve already seen str, which takes anything and returns a string representation of ...