01Python Basic _ 07 function, 01python_07 Function

01Python Basic _ 07 function, 01python_07 Function
1. define functions

1 def add(x, y):2     """Add two numbers.

　　　 The two values must be integers or strings"""　　#DocStrings3     a = x + y4     return a

DocStrings: the string of the first logical line of the function is the function'sDocument string. Note that DocStrings also applies to modules and classes. A document string is a multi-line string whose first line starts with an uppercase letter and ends with a full stop. The second line is empty, and the detailed description starts from the third line.

Return returns a specific value. If omitted, returnNone.

2. Set default parameters

When defining a function, you can set the default value of the parameter:

Def quad (x, a = 1, B = 0, c = 0): return a * x ** 2 + B * x + cprint quad (2.0) # omit parameters with default parameters and assign only values to x

Out: 4.0

Print quad (2.0, B = 3) # assign values to parameters with default parameters

Out: 10

3. Accept indefinite Parameters

Def add (x, * args): # The parameter after x is treated as the element total = x for arg in args: total + = arg return totalprint add (1, 2, 3, 4) # it can be understood as: 1, (2, 3, 4) print add (1, 2)

Out: 10

3

You can also use keywords to input parameters:

Def add (x, ** kwargs): # ** kwargs is equivalent to a dictionary of total = x for arg, value in kwargs. items (): print "adding", arg total + = value return totalprint add (10, y = 11, z = 12, w = 13) # it can be understood as: 10, {y: 11, z: 12, w: 13}

Out: adding y

Adding z

Adding w

46

4. Input tuples and dictionaries

Def add (x, y): "" Add two numbers "a = x + y return a z = (2, 3) print add (* z) # "*" required w = {'X': 2, 'y': 3} print add (** w) # "**" Required

5. map Method generation Sequence

You can usemapUsing functions to generate sequences:

def sqr(x):     return x ** 2a = [2,3,4]print map(sqr, a)

Out: [4, 9, 16]

Based on the number of function parameters,mapMultiple groups of sequences are acceptable:

def add(x, y):     return x + ya = (2,3,4)b = [10,5,3]print map(add,a,b)

Out: [12, 8, 7]