[Go_on]2017-1-18 Python Basics

1. Notepad can set-preferences-language-tab to spaces

2. Editor recommended Sublime

3. Data type:

3.1 If there are many characters in the string that need to be escaped, you need to add a lot \ , in order to simplify, Python also allows r‘‘ ‘‘ the expression of the internal string default is not escaped;

3.2 If there is a lot of line wrapping inside the string, \n writing in a row is not good to read, in order to simplify, Python allows ‘‘‘...‘‘‘ the format to express multiple lines of content;

3.3 with and OR or not

3.4 Null is a special value in Python, None denoted by. Nonecannot be understood as 0 , because 0 it is meaningful, and None is a special null value.

In addition, Python provides a variety of data types such as lists, dictionaries, and also allows you to create custom data types;

3.5 in Python, an equal sign = is an assignment statement that assigns any data type to a variable, the same variable can be repeatedly assigned, and can be a variable of different types--the characteristics of a dynamic language

In Python, constants are typically represented in all uppercase variable names: But constants are still variables, and Python has no mechanism to guarantee that they are not changed--using all uppercase variable names to represent constants is only a customary usage.

3.6 // , called the floor, takes only the integer part of the result, rounding down

4. String & Encoding:

4.1 Unicode (computer memory usage)--utf-8 (Unicode compression type, hard disk, transport)--ascii (subset of Unicode\utf-8)

4.2 In the latest version of Python 3, the strings are encoded in Unicode;

For the encoding of a single character, Python provides an ord() integer representation of the function to get the character, and the chr() function converts the encoding to the corresponding character;

Because the Python string type is str , in memory, in Unicode, one character corresponds to a number of bytes.

If you want to transfer on a network, or save to disk, you need to turn it str into bytes bytes .

Python bytes uses b a prefixed single or double quotation mark for data of type:x = b‘ABC‘

Be aware of the distinction ‘ABC‘ and the b‘ABC‘ former is str that although the content is displayed in the same way as the former, bytes each character occupies only one byte.

The pass-through method that is represented in Unicode str encode() can be encoded as a specifiedbytes----要把bytes变为str，就需要用decode()方法

The 4.3 len() function calculates the str number of characters, and if bytes so, the len() function calculates the number of bytes:

4.4 Formatting

%d	integers (formatted integers and floating-point numbers can also specify whether to fill 0 and integers with decimals)
%f	Floating point number
%s	String ( %s always works, it converts any data type to a string, which is used %% to represent one % )
%x	hexadecimal integer

[Go_on]2017-1-18 Python Basics