Python 个人笔记

Python 笔记

• hello world

print("hello world!")

• print 换行符

print('hello 
 world')

• print 行结束符

print('hello 
 world', end='?')

• 基础数据类型

a = 6
b = 1.34
c = True
d = 'hello world'

• 变量命名规范

  1. 数字 字母 下划线

  2. 不能以数字开头

  3. 不能使用保留字

  4. 严格区分大小写

     保留字
     from	imort	as
     True	False	None
     class	pass	with
     def	yield	retrun
     if	elif	else
     for	while	continue	break
     try	raise	except	assert	finally
     is	not	in	and	or
     labmda	del	global	nonlocal

• 复合数据类型

list 列表

ls = [6, 1.34, True, 'alex']

tuple 元组

tl = [6, 1.34, True, 'alex']

dict 字典

dl = [6, 1.34, True, 'alex']

set 集合

st = [6, 1.34, True, 'alex']

• 运算符

• 格式化字符串

  python 3.6 以后支持 f-string format的简化版本

  print(f'name is {name}, age is {age}, alex age is {sta.age}')
  print(f'get {12*3+5}')
  print(F"name is {name:#<6s}, age is {age:3d}, weight is {weight:^9.2f}")
  print(F"name is {'davida':#<6s}, age is {111:3d}, weight is {123456.789:9.2f}")
  print(f'hex value {254:#X}')
  

  format 方式

  print('name is {:6s} next'.format(name))
  print('name is {:.3s}'.format(name))
  print('age is {:0>6d}'.format(age))
  print('age is {:0<6d}'.format(age))
  print('age is {:>6d}'.format(age))
  print('age is {:6d}'.format(age + 111))  # 默认是右对齐
  # print('age is {:>6d} next'.format(age+1))
  print('age is {:<6d} next'.format(age + 1))
  print('age is {:^6d} next'.format(age + 1))
  print('weight is {:+12.3f}'.format(weight))
  print('weight is {:.2%}'.format(weight / 120))
  print('id is {:6d}'.format(id))
  print('
  
  ')
  
  print('name is {}, age is {}'.format(name, age))
  print('name is {0}, age is {1}, name is {0}'.format(name, age))
  info_list = [name, age]
  print('name is {0[0]}, age is {0[1]}, name is {0[0]}'.format(info_list))
  
  print('name is {name}, age is {age}, name is {name}'.format(name=name, age=age))
  info_dict = {'name': name, 'age': age}
  print('name is {name:?>12s}, age is {age}, name is {name}'.format(**info_dict))
  
  class Student(object):
      def __init__(self, name, age):
          self.name = name
          self.age = age
  
  sta = Student('alex', 12)
  stb = Student('lucy', 11)
  print('alex name is {0.name}, lucy age is {1.age}'.format(sta, stb))
  

  % 方式: 变量和占位符一一对应,不够灵活

  print('age is %d' % age)
  print('age is %6d' % age)
  print('age is %11d' % age)
  print('age is %06d' % age)
  print('age is %011d' % age)
  
  print('name is %s' % name)
  print('name is %24s' % name)
  print('name is %.3s' % name)
  print('name is %a' % name)
  
  print('weight is %f' % weight)
  print('weight is %.2f' % weight)
  # %6.2f 表示总长度为6(包括小数点),保留2位小数
  print('weight is %6.2f' % weight)
  
  print('MULTI: name is %s, age is %d' % (name, age))
  print('MULTI: name is %s, age is %s' % (name, age))
  

• 转义字符

• 基础数据类型转换

• 复合数据类型转换 容器

• 字符串编码

• 赋值与引用的概念

• 运算符重载/公共操作

• 内置函数 基础

• print详解

• if

• for

• while

• def 函数定义

• def 参数

• def 函数说明信息

• lambda

• 内置函数 高阶

• 文件操作 open

• 面向对象 class

• 导入模块 from import as

• 内置模块 os

• 内置模块 time

• 内置模块 random

• 内置模块 json

• 内置模块 request

• 内置模块 urllib

• 列表推导式

• 字典推导式

• 集合推导式

• 常用模块 requests

• 常用模块 pandas

• 常用模块 pathlib