Python3 Fifth day (conditions, loops, functions)

If statement:

If condition 1:

..

Elif Condition 2:

..

Else

..

Each condition is followed by a colon to represent the statement to be executed after the condition is met.

While loop:

While condition:

...

While condition:

...

Else

...

For loop:

for Var in seq:

...

Else

...

Iterators have two basic methods: ITER () and Next ()

strings, lists, tuples, all can be used to create iterative objects

Create an Iterative object: ITER (List/string/tuple)

You can make a for loop on an iterative object, or you can use next to access the next element in the iteration object.

Function

definition of the function:

Defined by Def, followed by the function name, parentheses (), the parameters are defined in parentheses, with the colon happy function body.

def function name (parameter list):

function contents

[Return var] #当没有return语句时, function returns none

function must be defined before calling the

mutable types and immutable types

String,tuples,numbers is a non-modifiable object, List,dict,set is a modifiable object, for a variable of a non-modifiable object, when the function argument is passed, the value of the object is modified, not the object itself.

Parameters:

Required parameters, keyword parameters, default parameters, indeterminate length parameters

Required parameters: The parameters must be in the correct incoming order, and the number should be the same.

Keyword parameter: match parameter value by parameter name, e.g. func (age=12,name= ' 2222 ')

Default parameter: def func (name,age=12), called when the value of the age parameter, can not be passed.

Indefinite length parameter: def func ([Arg,] *var_args_tuple), with the asterisk (*) variable name, which holds all the unnamed variable arguments.

Anonymous functions:

Using lambda to define anonymous functions

Lambda has its own namespace and cannot access arguments outside of an expression and variables in the global namespace

Grammar:

Lambda arg[,arg[,arg....]]:express

such as Lambda Arg1,arg2:arg1*arg2. Returns the product of a two parameter

Variable scope:

There are four types of scopes:

L (local) Local

In functions outside of the E (enclosing) closure function

G (Global) overall

B (built-in) built-in

Variable lookup rules l->e->g->b, ranging from small to large lookups

Only Module,class,def Lambda will introduce a new scope.

Global and nonlocal:

To use global Var to re-declare variables when an internal scope modifies an external scope variable

When modifying variables in nested scopes (the scope of enclosing), use nonlocal var to re-declare variables

Python3 Fifth day (conditions, loops, functions)