3rd Python functions and file operations

Function

Defined

1. Basic structure

Def func_name ():

Func_code

2. Three different forms

No parameters: The scenario simply performs some action, such as interacting with the user, printing

Parameter: It is necessary to perform the corresponding logic, such as statistical length, to calculate the maximum minimum value, according to the parameters passed in externally.

Empty function: Design code structure

3. Function only detects syntax in the definition phase, does not execute code

Call

Func_name ()

List parameter call/keyword argument call (keyword argument behind)

Attention:

1. function is defined first and then called

2 The definition of a function is similar to the definition of a variable, without defining the variable beforehand, and directly referring to the variable, the error does not define the function beforehand, and the direct call is equivalent to referencing a nonexistent variable name

Parameters:

#形参: When defining a function, the parameters inside the parentheses become formal parameters

#特点: A parameter is a variable name

# def foo (x, y): #x =1,y=2

# Print (x)

# Print (y)

#实参: When a function is called, the arguments inside the parentheses become arguments

#特点: argument is a variable value

# foo (ON)

#在调用阶段实参 (variable value) to bind formal parameter (variable name)

#调用结束后, Unbind

Return value: Return value does not have a type limit

1. No return: Return none, equivalent to return none

2. Return a value: Returns the value

3. Return Val1,val2,val3: Return (VAL1,VAL2,VAL3)

1. Function name + function body

2. Input (parameter)/output

3. Parameter defaults (default parameters must be behind)

def func_name (param1, param2, Param3, ..., param_m=default_m, ..., param_n=default_n):

Func_code1

Func_code2

...

Func_coden

Return Return_value

Func_name (value1, value2, Value3, ..., value_m-1, [Value_m, ..., Value_n])

LGB Principles

L = local (locally)

G = Global (overall)

B = Builtin (built-in)

In accessing a variable is Python looking for the order is l->g->b

Variable parameters

List/Dictionary

def func_name1 (*args, **kwargs):

Print args, Kwargs

def func_name2 (*args):

Print args

def func_name3 (**kwargs):

Print Kwargs

function is also a variable

A list of the squares of all elements in range (0, 10)

RT = []

For I in range (10):

Rt.append (i * i)

[I * I for I in range (10)]

A list of the squares of all even-numbered elements in range (0, 10)

RT = []

For I in range (10):

If I% 2 = = 0:

Rt.append (i * i)

3rd Python functions and file operations