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Special Case–a list with a default value
When the optional parameter is a list. Its value remains from the last function call. To prevent this, the list parameter must initialize inside the function's body.Examples :
| Call with inherit | Call without inherit |
| def fct(A,L=[]): L.append(A) return L >>>print fct("toto") ['toto'] >>>print fct("titi") ['toto', 'titi'] >>>print fct(3) ['toto', 'titi', 3] >>>print fct("titi",[]) ['titi'] | def fct(A,L=None): if L is None : L=[] L.append(A) return L >>>print fct("toto") ['toto'] >>>print fct("titi") ['titi'] >>>print fct(3) [3] >>>print fct("titi",[]) ['titi'] |
Function call
The ways to call a function are:- Use all parameters in they order.
- Without use all optional parameters.
- explicitly naming the parameter.
| All in order | Without optional parameter | Called parameter |
| def fct(A,B=0,C=1) : return (A+B)*C >>> print fct(5,3,2) 16 | def fct(A,B=0,C=1) : return (A+B)*C >>> print fct(2,5) 7 | def fct(A,B=0,C=1) : return (A+B)*C >>> print fct(2,c=2) 4 >>> print fct(a=2,c=2) 4 |
Get the function's documentation
The user can easily access the function documentation, if off course the programmer has coded it.Example :
| def square(A) : """Function square compute the square of a value Entry Parameter: First the Value to square. Return Value The square of the first parameter. """ return A*A >>>print square.__doc__ # __ contents 2 underscores Function square computes the square of a value Entry Parameter: First the Value to square. Return Value The square of the first parameter. >>>print square(5) 25 |
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