Python builtin methods or functions description using Python

builtin_method_python.md

• Example of Python function: int()
• Show the internal methods of int:

  dir(int)
  

  # Output:
  ['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']
  

• Show the docstring of int:

  print(int.__doc__)
  
  # Output
  int(x=0) -> integer
  int(x, base=10) -> integer
  
  Convert a number or string to an integer, or return 0 if no arguments
  are given.  If x is a number, return x.__int__().  For floating point
  numbers, this truncates towards zero.
  
  If x is not a number or if base is given, then x must be a string,
  bytes, or bytearray instance representing an integer literal in the
  given base.  The literal can be preceded by '+' or '-' and be surrounded
  by whitespace.  The base defaults to 10.  Valid bases are 0 and 2-36.
  Base 0 means to interpret the base from the string as an integer literal.
  >>> int('0b100', base=0)
  4
  

• List the exceptions thrown by the method:

  import re
  re.findall(r'\w+Error', int.__doc__)
  # Output: []
  
  re.findall(r'\w+Error', open.__doc__)
  # Output: ['IOError', 'FileExistsError', 'ValueError']
  

int('0b100', base=0)

How is that possible? Isn't base 0 disallowed?