Python basic syntax

Python basic syntax

The Python language has many similarities with languages such as Perl,c and Java. However, there are some differences.

In this chapter we will learn the basic syntax of Python in the future

Interactive programming

Interactive programming does not require creating scripts, but rather writing code through the Python interpreter interaction pattern.

Pythonpython 2.7.6 (default, Sep 9, 15:04:36) [GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on Darwintype " Help "," copyright "," credits "or" license "for more information.>>>

Installing the interactive client on Windows

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Enter the information in the Python prompt

>>> print "Hello, python!";

In the Python 2.7.1 the output is

Hello, python!.

Print: Multiple characters can be printed for channeling, separated by a string of outputs

Print (a), (b), (? ）

Enter information in the Python prompt (version issue high version requires plus () otherwise error)

>>> print ' A ', ' B ', '? ';

Displayed as

A B?

Python identifiers

In Python, identifiers are composed of letters, numbers, and underscores.

In Python, all identifiers can include English, numeric, and underscore (_), but cannot begin with a number.

Identifiers in Python are case-sensitive.

Identifiers that begin with an underscore are of special significance. A class attribute that begins with a single underscore (_foo) cannot be accessed directly, and is accessed through the interface provided by the class and cannot be imported with "from XXX import *";

A double underscore (__foo) represents a private member of a class; a double underscore (__foo__) represents a special method-specific identifier for Python, such as __init__ (), which represents the constructor of a class.

Variable

What is a variable:

One can be variable value

The variables in the program are purely in memory to open up a place where the data can be stored, and then seven names, the name is the variable

Variables can store any data, variable declarations must be assigned values

Variable name can be people have to go, must be case in English, numeric underline, can not start with numbers

Define variables A and B to assign values separately

>>> a=123

>>> B=sam

Output variable View results

>>> Print a

123

>>> Print B

Sam

>>>

Variable characteristics, variable itself type is not fixed, Python dynamic language, the advantages of more flexible

Defining strings in Python

‘’“”

If the middle character is channeling ' "', you can use the translator \\\\\\\\\

>>> a= ' 123 '

>>> b= ' 1 '

Run an error after defining the string

>>> Print A*b

Traceback (most recent):

File "<pyshell#22>", line 1, in <module>

Print A*b

Typeerror:can ' t multiply sequence by non-int of type ' str '

Undefined string to display normally

>>> a=1

>>> b=2

>>> Print A*b

2

-----------------------------------------------------------------------------------------------the delimiter of one ear

Look at the list.

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Python basic syntax