python variables and data type

variable

Variable definition:

In the process, sometimes we need two data summation, then how to do it?

We analogies about real life, such as going to the supermarket to buy things, we often need a basket, used to store items until all items are buying is completed, you can checkout at the cash register

If a program requires data to two or more data summing, then it is necessary to store these data to stand, and then they can be added together

In python, a data storage, requires called variable things, the following example:

num1 is a variable, like a small basket

num2 is also a variable

ret = num1 + num2 # num1 and num2 data two "basket" in the accumulated, then into variable ret

Description:

The so-called variable , can be understood as basket, if you need to store more data, the easiest way is to have a number of variables, of course you can also use a

Procedure is used to process the data, and the variable is used to store data

Type of the variable

View variable data types

How do I know the type of a variable of it?

In python, as long as the definition of a variable, and it has data, then its type has been identified, we do not need the developer's initiative to explain its type, the system will automatically identify

You can use type (variable's name), to see the type of a variable

Identifier

Life identifier

What is the identifier?

Some of the symbols and names of developers in a program custom

Identifier own definition, such as variable names, function names, etc.

Identifier naming rules:

Identifier can only consist of letters, underscore "_" numbers
Identifiers can not begin with a number
Identifier can not use the keyword (keyword not the same name in python), but may contain critical

Identifier naming suggestions:

Identifier naming should "see to know the name meaning"

python keywords

python some of the special features of the identifier, which is called keyword

Keyword, python is already in use, so do not allow developers to define their own name and the same keywords as identifiers

Think about what substandard following identifiers

if、name、and、my_list、my_list1、from#1、age、2list、as、True、wetyui、height、my_log、qwe&qwe

Identified by letters, underscores and numbers, and the numbers can not start, must be unique keyword

python identifier is case sensitive

Example: BaoBao not equal baobao, bao not equal Bao

Identifier naming

Underline:

There is also a nomenclature with an underscore "_" to connect all the words, for example:

my_list、user_name

Identifier naming

Hump nomenclature:

Small camel nomenclature (lower camel case): the first word beginning with a lowercase letter; the first letter of the second word is capitalized, for example: myName, myList

Large camel nomenclature (upper camel case): the first letter of each word in capital letters are used, for example: UserName, FirstName, LastName

Export

Life in the output:

Software output:

python output variables:

Formatted output

The purpose of formatting operation:

For example, we have the following code:

Think about it: when the output of age, with a number of "I am xx years old," and it can simplify procedures? ? ?

A: The output format can be done

Formatted output

What is formatted output, see the following code:

Formatted output

In the program, such as% saw operator, the output of which is formatted in python

The formatted output common format symbols

The formatted output format common practice notation

The general format identifier formatted output Examples Introduction

The formatted output transducer output line

Wrap output: when output if there \ n So, at this time \ n after the content is displayed in another row

as the picture shows:

Entry

When we withdraw money before the bank ATM machine, be sure to enter the password, is not it?

So how can let the program know what we just entered it? ?

We should know, if you want to complete the ATM machine to withdraw money this thing, you need to enter data start with a keyboard, and then save with a variable, is not it easier to understand? ? ?

However, the input python2.x and python3.x or differentiated?

python2.x input is such that: raw_input ()

python3.x input is such that: input ()

Python3.x here for an example: