# learn_python

**Repository Path**: xuliangbo/learn_python

## Basic Information

- **Project Name**: learn_python
- **Description**: learn_python<python  程序设计 第三版>跟练
- **Primary Language**: Python
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 9
- **Forks**: 1
- **Created**: 2020-07-18
- **Last Updated**: 2023-07-12

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Python基础

 > python3支持 `UTF-8` 字符集，python区分大小写。
 > python2支持中文较差 需要再文件头 `#coding:utf-8`
 
 ### print函数
 ```python
 #变量是真的变量，动态类型
 name = 'King'
 #合法的
 name = 787
 
 #print a,b,c必须都是str
 print(a,b,c) 
 
 #需求帮助的方法
 #python3进入控制台后，
 >>>help(print)
 
 Help on built-in function print in module builtins:

    print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    
    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.
    
#不用默认的空格‘ ’分割可  改成 ‘｜’分割    
print(a,b,c,sep = '|')     

print(a,b,c,sep='|',end = '') 
# \n \t  \' 转移字符  
>>> print('乔治说：\'我要吃饭\'  ')
乔治说：'我要吃饭' 


#输入代码对比结果：
#  r 代表 内部字符串默认不转义
print('乔治说：“想吃饭”')
print('\ahahah')
print('hello\py\\thon')
print('hello\py\thon')
#结果
-bash-3.2$ python3 chapter001.py 
乔治说：“想吃饭”
hahah
hello\py\thon
hello\py	hon

#占位符用法 %d  %f   %.2f
a='徐'
b='亮'
c='波'

print('添加了%s,12%s1213%s' % (a,b,c))
添加了徐,12亮1213波
#
print('{}asdasd{}asda{}'.format(a,b,c))
print('添加了%s,12%s1213%s' % (a,b,c))
# 

 ```
 
 ### 比较运算
 
 > 控制器中的 -5～～256 的值 会保存在同一个内存地址，大数值不会
 
 ```python
 
a = 10
b = 10
print(a is b)
print(a == b)

c = 2000000
d = 2000000
print(c is d)
print(c == d)


## is 相当于 id(a) == id(b)

print(id(c))
print(id(d))

 # 幂运算符
print(2**8)

print("*" * 30)
print('\t\thahaha')
print("*" * 30)
# 输出
256
******************************
		hahaha
******************************

# 精确的
a = 9/4
# 地板除
b = 9//4

 ```
 
 ### and  or  not
 
 
 ####  三元运算符
 ```
 (a+b) if a > b else (a-b)
 ```
 
 ##### 缩紧 对应 if条件执行语句
 ```
 # ''  0  None 默认是False
 username = 'king'
 if username:
    print('alskdjla')
    
// 以️：结束时 缩进语句视为 代码块   
if(3<4):
    xxx
elif 5>6:
    sss
else:
    pass
 
 ```
 ### range函数
 ```
 range(0,50,5)
 class range(object)
 |  range(stop) -> range object
 |  range(start, stop[, step]) -> range object
 |  
 |  Return an object that produces a sequence of integers from start (inclusive)
 |  to stop (exclusive) by step.  range(i, j) produces i, i+1, i+2, ..., j-1.
 |  start defaults to 0, and stop is omitted!  range(4) produces 0, 1, 2, 3.
 |  These are exactly the valid indices for a list of 4 elements.
 |  When step is given, it specifies the increment (or decrement).
 |  
 |  Methods defined here:
 |  
 |  __bool__(self, /)
 |      self != 0
 |  
 |  __contains__(self, key, /)
 |      Return key in self.
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __getitem__(self, key, /)
 |      Return self[key].
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __hash__(self, /)
 |      Return hash(self).
 |  
 |  __iter__(self, /)
 |      Implement iter(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __len__(self, /)
 |      Return len(self).
 |  
 |  __lt__(self, value, /)
 |      Return self<value.
 |  
 |  __ne__(self, value, /)
 |      Return self!=value.
 |  
 |  __reduce__(...)
 |      Helper for pickle.
 |  
 |  __repr__(self, /)
 |      Return repr(self).
 |  
 |  __reversed__(...)
 |      Return a reverse iterator.
 |  
 |  count(...)
 |      rangeobject.count(value) -> integer -- return number of occurrences of value
 |  
 |  index(...)
 |      rangeobject.index(value) -> integer -- return index of value.
 |      Raise ValueError if the value is not present.
 |  
 |  ----------------------------------------------------------------------
 |  Static methods defined here:
 |  
 |  __new__(*args, **kwargs) from builtins.type
:

 ```
 
 ```
 for i in  range(20):
    print('hello')
 ```
 
 #### chmod 
 ```
 u 表示该文件的拥有者，g 表示与该文件的拥有者属于同一个群体(group)者，o 表示其他以外的人，a 表示这三者皆是。
 + 加号 表示增加权限、- 表示取消权限、= 表示唯一设定权限。
r 表示可读取，w 表示可写入，x 表示可执行，X 表示只有当该文件是个子目录或者该文件已经被设定过为可执行。
 ```
 ```
 chmod a+x hello.py
 
 ```
 
 ## 字符
 ```
 ord('A')
 
 chr(66)
 chr(25991)
 
 'ABC'.encode('ascii')
 
 ```