parameter matching for Python functions

Version: General use python2.7.6

python3.4.3 will mark

1. Immutable objects (integers, strings) are passed through an object reference and cannot be changed inside the function.

1 def F (a): 2 ...     a=10034 >>> b=885 >>> f (b)6 >>> b 7 88

2. mutable objects (lists, dictionaries) are also passed through an object reference and can be changed inside the function. (The original object is changed locally, but the re-assignment does not change)

 1  >>> def   F (a):  2  ... a=[1,2,3 3   ...  4  >>> b=[]  5  >>> F (b)  6  >> > b  7  [] 

1 def F (a): 2 ...     A.append (3)34 >>> F (b)5 >>> b 6 [3]

3. Parameter matching

Default parameters and keyword parameters

1>>>defF (a):2... a.append (3)3 ... 4>>>F (b)5>>>b6[3]7>>>8 Keyboardinterrupt9>>>defF (a,b,c):Ten...Print(a,b,c) One ...  A>>> F (A) -(1, 2, 3) ->>> F (c=3,a=1,b=2) the(1, 2, 3) ->>>defF (a,b=2,c=3): -...Print(a,b,c) - ...  +>>> F (1,4) -(1, 4, 3)

4. Arbitrary parameter Matching

* and * * Support any number of parameters

* Collect parameters into a tuple.

1>>>defF (*arges):2...Print(Arges)3 ...4>>> F (1,'a',['2', 3],{'a': 1,'b': 2})5(1,'a', ['2', 3], {'a': 1,'b': 2})

* * Valid only for keyword arguments, pass keyword arguments to a dictionary, and then work in a dictionary.

1>>>defF (* *arges):2...Print(Arges)3 ... 4>>>F ()5 {}6>>> F (a:1)7File"<stdin>", Line 18F (a:1)9^Ten syntaxerror:invalid Syntax One>>> F (a=1,b=2) A{'a': 1,'b': 2} ->>> F (1=a,2=b) -File"<stdin>", Line 1 theSyntaxerror:keyword can'T is an expression ->>> F ('1'=a,'2'=b) -File"<stdin>", Line 1 -Syntaxerror:keyword can'T is an expression +>>> F (1='a', 2 ='b') -File"<stdin>", Line 1 +Syntaxerror:keyword can'T is an expression A>>> F ('a'=1,'b'=2) atFile"<stdin>", Line 1 -Syntaxerror:keyword can'T is an expression ->>> F (a=1,b=2) -{'a': 1,'b': 2} ->>> F (a=[1],b=2) -{'a': [1],'b': 2} in>>>

The form of multiple parameters can be passed

1>>>defF (*a,**b):2...Print(A, b)3 ...4>>> F (1,'a', [3,3],x=1,y='e')5((1,'a', [3, 3]), {'y':'e','x': 1})

1>>>defF (a,*b,**c):2...Print(a,b,c)3 ... 4>>> F ('s','s','s', s='s')5('s', ('s','s'), {'s':'s'})6>>>

The second and third ' s ' above are collected into a tuple

Only keyword parameters (Python3 or more) can be used.

1 def F (a,*b,c):2     ... Print (a,b,c) 3  4 >>> F (,'a', c=3)5'  a') 3

1 def F (a,*, b,c):2     ... Print (a,b,c) 3  4 >>> F (1,b='a', c=3)5 1 a 3

The first example of the keyword C after *b must be assigned using the C=3 equation method

The second example * after B and C must use the equation to assign the value of the way

parameter matching for Python functions