一、控制文件内指针的移动
# f.seek(字节个数,模式)
# 模式有三种
# 0：参照文件的开头
# 1：参照当前所在的位置
# 2：参照文件末尾的位置
# 注意：
# 1、无论何种模式，都是以字节单位移动,只有t模式下的read(n)的n代表的是字符个数
# with open('a.txt',mode='rt',encoding='utf-8') as f:
# data=f.read(6)
# print(data)
# with open('a.txt',mode='rt',encoding='utf-8') as f:
# data = f.read(6)
# print(data)
# with open('a.txt',mode='rt',encoding='utf-8') as f:
# data = f.read(6)
# print(data) #打印的是字符hello美
# with open('a.txt',mode='rb') as f:
# data = f.read(6)
# print(data) #显示的是字节b'helloxe7'
# with open('a.txt',mode='rb')as f:
# data = f.read(6)
# print(data)
# with open('a.txt',mode='rb') as f:
# data=f.read(5)
# print(data.decode('utf-8'))
# with open('a.txt',mode='rb',)as f:
# data = f.read(5)
# print(data.decode('utf-8'))
# with open('a.txt',mode='rb') as f:
# data = f.read(5)
# print(data.decode('utf-8'))
# with open('a.txt',mode='rb') as f:
# data = f.read(5)
# print(data.decode('utf-8'))
# 2、只有0模式可以在t模式下使用，而0、1、2都可以在b模式下用
# 示例
# with open('a.txt',mode='rt',encoding='utf-8') as f: #t模式下1,2模式会报错
# f.seek(3,2)
# with open('a.txt',mode='rb',encoding='utf-8') as f:
# f.seek(0,0)
# with open('a.txt',mode='rb') as f:
# f.seek(6,0)
# print(f.read().decode('utf-8'))
# f.seek(16,1)
# print(f.tell())
# with open('a.txt',mode='rb')as f:
# f.seek(5,0)
# print(f.read().decode('utf-8'))
# with open('a.txt',mode='rb') as f:
# f.seek(8,0)
# print(f.read().decode('utf-8'))
# f.seek(19,1)
# print(f.tell())
# f.seek(-3,2)
# print(f.read().decode('utf-8'))
# f.seek(0,2)
# print(f.tell())
# with open('b.txt',mode='wt',encoding='utf-8') as f:
# f.seek(10,0)
# print(f.tell())
# f.write("你好")
# 应用1：tail -f access.log
# import time
# with open('access.log',mode='rb') as f:
# f.seek(0,2)
# while True:
# line=f.readline()
# if len(line) == 0:
# time.sleep(0.3)
# else:
# print(line.decode('utf-8'),end='')
# import time
# with open('abuse.log',mode='rb')as f:
# f.seek(0,2)
# while True:
# line = f.readline()
# if len(line) == 0:
# time.sleep(0.3)
# else:
# print(line.decode('utf-8'),end='')
run.py
# import time
#
# with open('access.log',mode='at',encoding='utf-8') as f:
# f.write("%s %s
" %(time.strftime("%Y-%m-%d %H:%M:%S %p"),"egon给alex转了3个亿"))
# import time
# with open('abuse.log',mode='at',encoding='utf-8')as f:
# f.write('%s %s
'%(time.strftime('%Y-%m-%d %H:%M%S%p'),'吴常文给姜高转了一百个亿'))
二、文件操作的其他方法
# with open('b.txt',mode='rt',encoding='utf-8') as f:
# data=f.readlines()
# print(data,end=' ')
# print()
with open('b.txt',mode='wt',encoding='utf-8') as f:
# f.write("1111
222
3333
")
lines=["aaaa
",'bbb
','cccc
']
# for line in lines:
# f.write(line)
#
# f.writelines(lines)
# f.writelines("hello")
# f.write("hello")
# with open('b.txt',mode='wt',encoding='utf-8') as f:
# f.write('hello
')
# f.write('world
')
# f.flush()
with open('b.txt',mode='r+t',encoding='utf-8') as f:
f.truncate(4)
三、可变长参数
def index(x,y,z):
print(x,y,z)
def wrapper(*args,**kwargs): # args=(1,2,3,4,5) kwargs={"a":1,"b":2}
index(*args,**kwargs) # index(*(1,2,3,4,5),**{"a":1,"b":2})
# index(1,2,3,4,5,a=1,b=2)
# index(x=1,y=2,z=3)
wrapper(x=1,y=2,z=3)
四、函数对象
# 函数是第一个等公民：可以把函数当变量去用
def func(): # func=函数的内存地址
print('from func')
x=10 # x=10的内地址
#1、可以被赋值
# f=func
# f()
#2、可以当作参数传给另外一个函数
# def foo(f):
# print(f)
# f()
#
# foo(func)
#3、可以当作函数的返回值
# def foo(f):
# return f
# res=foo(func)
# print(res)
#4、可以当作容器类型的元素
# l=[func,]
# print(l)
# l[0]()
def login():
print('登录...')
def register():
print('注册...')
def tranfer():
print('转账...')
def withdraw():
print("提现功能。。。")
func_dic={
"1":["登录",login],
"2":["注册",register],
"3":["转账",tranfer],
"4":["提现",withdraw]
}
while True:
for k,v in func_dic.items():
print(k,v[0])
choice = input("请输入您的命令编号，输入0退出：").strip()
if choice == "0":
break
if choice in func_dic:
func_dic[choice][1]()
else:
print("输入的指令错误")
五、补充
def add(x:int,y:int) -> int:
return x+y
# res=add("aaa","bbbb")
# print(res)
# help(add)
六、函数嵌套
# 1、函数的嵌套调用：在调用一个函数的过程中又调用了其他函数
# def bar():
# print('from bar')
#
# def foo():
# print('from foo')
# bar()
#
# foo()
# 应用示例
# def max2(x,y):
# if x > y:
# return x
# else:
# return y
#
# def max4(a,b,c,d):
# res1=max2(a,b)
# res2=max2(res1,c)
# res3=max2(res2,d)
# return res3
#
# print(max4(1,2,3,4))
# 2、函数的嵌套定义：在一个函数内部又定义了其他函数
# 特点：定义在函数内的函数通常情况只能函数内部使用，这是一种封闭的效果
# def f1():
# def f2():
# print('from f2')
#
# x = 111
# # print(x)
# # print(f2)
# f2()
# f1()
# 应用示例
# from math import pi
#
# def circle(radius,action=1):
# def perimeter(radius):
# return 2 * pi * radius
#
# def area(radius):
# return pi * (radius * radius)
#
# if action == 1:
# return perimeter(radius)
# elif action == 2:
# return area(radius)
#
# print(circle(10,1))
# print(circle(10,2))
# 函数嵌套定义+函数对象
def f1():
def f2():
print('from f2')
return f2
res=f1()
print(res)
res()
七、名称空间与作用域
# 一：名称空间：就是用来存放名字的内存空间
# 名称空间分为三大类：
# 1、内置名称空间：存放python解释器提供的名字
# 生命周期：python解释器启动则产生，python解释器关闭则销毁
# 2、全局名称空间：顶级的名字
# 生命周期：开始python程序则启动，python程序运行完毕则销毁
# x = 1
# y = 2
# if True:
# z = 3
#
# while True:
# bbb = 44
#
# 3、局部名称空间：在函数内部定义的名字
# 生命周期：调用函数则产生，函数调用结束则会立即销毁
# def f1(aaa):
# # aaa=555
# def f2():
# ccc = 666
#
# f1(555)
# 名字访问的优先级：基于当前所在的位置向上查找（局部-》全局-》内置）
# 例1
# # len=111
#
# def f1():
# # len=222
# def f2():
# # len=333
# print(len)
# f2()
#
# f1()
# 例2
# def f1():
# print(len)
#
# # f1()
# len=111
# # f1()
#
# def foo():
# len=333333
# f1()
#
#
# def bar():
# len=44444
# f1()
#
# foo()
# bar()
# 例3:
# aaa=333
#
# def f1():
# # print(aaa)
# # print(len)
# x=111
# def ff1():
# print("fff1===>x: ",x)
# ff1()
#
# def f2():
# # print(aaa)
# # print(len)
# y=222
#
# f1()
# f2()
#
# 例4：
# len=111
#
# def f1():
# print(len)
#
#
#
# def f2():
# len=33333333333333333333
# f1()
#
# f2()
# 名称空间的嵌套关系是在函数定义阶段扫描语法的时候生成的
# x=111
#
# def func():
# print(x)
# y=2222
#
# func()
# 二：作用域
# 全局作用域：内置+全局名称空间中的名字
# 特点：全局存活、全局有效
# 局部作用域：局部名称空间空间的名字
# 特点：临时存活，局部有效
# LEGB
# 三：global、nonlocal
# 3.1 global:在函数内声明名字是来自于全局的
# l=[1,2,3]
# def func():
# l[0]=111
# func()
# print(l)
# x=10
# def func():
# global x
# x=20
# func()
# print(x)
# 3.2 nonlocal在函数内声明名字是来自于外层函数的
# x=333
# def f1():
# # x=111
# def f2():
# # global x
# nonlocal x
# x=222
# f2()
# print(x)
#
# f1()
def f1():
x=111
def f2():
print('from f2',x)
return f2
res=f1()
def foo():
x=222
res()
foo()
八、闭包函数
# 闭包函数=函数嵌套定义+名称空间与作用域+函数对象
# 闭：指的是该函数是一个定义在函数内部的函数
# 包：闭函数访问了一个来自于外层函数中的名字
# def f1():
# x = 111
# def f2():
# print('from f2: ',x)
#
# return f2 # 千万不要加括号
#
# res=f1()
#
# def foo():
# x=222
# res()
#
# foo()
# 为函数体传参的解决方案：
# 方案一：直接定义形参
# def f2(x):
# print(x)
#
# f2(111)
# f2(222)
# f2(333)
# 闭包函数是一种为函数体传参的解决方案
# def f1(x):
# # x=111
# def f2():
# print(x)
#
# return f2 # return f1.locals.f2的内存地址
#
# f2=f1(111)
# f2()
# 写死？
# 专用？
# 传值？
def outter(x):
# x =2222
def wrapper():
print(x)
return wrapper
f=outter(333)
# print(f)
f()
九、装饰器
"""
1 什么是装饰器
器=》工具=》函数
装饰=》指的是为被装饰者添加新功能
2、为何要用装饰器
开放封闭原则：
封闭指的是对修改源代码是封闭的
开放指的是对拓展新功能是开放的
装饰器就是一个函数，该函数就是在不修改被装饰对象源代码以及调用的方式的前提下，为被装饰对象添加额外的功能
3、如何实现装饰器=》闭包函数
装饰器的目标：为被装饰对象添加额外的新功能
装饰器的实现应该遵循的原则：
1、不该被装饰对象的源代码
2、不该被装饰对象的调用方式
"""
# # 例1：
# import time
#
# def index():
# start=time.time()
# print("index===>")
# time.sleep(0.5)
# stop=time.time()
# print("run time is : %s" %(stop - start))
#
# index()
# # 例2：
# import time
#
# def index():
# print("index===>")
# time.sleep(0.5)
#
#
# start=time.time()
# index()
# stop=time.time()
# print("run time is : %s" %(stop - start))
# # 例3：
# import time
#
# def index():
# print("index===>")
# time.sleep(0.5)
#
#
# def wrapper():
# start=time.time()
# index()
# stop=time.time()
# print("run time is : %s" %(stop - start))
#
# wrapper()
# # 例4：直接通过参数为函数体传参
# # import time
# #
# # def index():
# # print("index===>")
# # time.sleep(0.5)
# #
# #
# # def wrapper(func):
# # start=time.time()
# # func()
# # stop=time.time()
# # print("run time is : %s" %(stop - start))
# #
# # wrapper(index)
# # 例5：直接通过参数为函数体传参
# import time
#
# def index():
# print("index===>")
# time.sleep(0.5)
#
#
# def outter(func):
# # func=index的内存地址
# def wrapper():
# start=time.time()
# func()
# stop=time.time()
# print("run time is : %s" %(stop - start))
# return wrapper # 千万不要加括号
#
# index=outter(index)
#
# index() # wrapper()
# 例6：
# import time
#
# def index(x,y,z):
# print("index===>",x,y,z)
# time.sleep(0.5)
# return 123
#
# def home(name):
# print('welcome %s to home page' %name)
# time.sleep(1)
#
# # index(1,2,3)
# # home("egon")
#
# def outter(func):
# # func=index的内存地址
# def wrapper(*args,**kwargs):
# start=time.time()
# res=func(*args,**kwargs)
# stop=time.time()
# print("run time is : %s" %(stop - start))
# return res
# return wrapper # 千万不要加括号
#
# index=outter(index)
# res=index(1,2,3) # wrapper(1,2,3)
# print(res)
#
# home=outter(home)
# res=home("egon")
# print(res)
# 例7：语法糖
# import time
# from functools import wraps
#
# def timmer(func):
# @wraps(func)
# def wrapper(*args,**kwargs):
# start=time.time()
# res=func(*args,**kwargs)
# stop=time.time()
# print("run time is : %s" %(stop - start))
# return res
# # wrapper.__name__=func.__name__
# # wrapper.__doc__=func.__doc__
# return wrapper # 千万不要加括号
#
# @timmer # index=timmer(index)
# def index(x,y,z):
# """
# index的文档注释
# """
# print("index===>",x,y,z)
# time.sleep(0.5)
# return 123
#
# @timmer # home=timmer(home)
# def home(name):
# """
# home的文档注释
# """
# print('welcome %s to home page' %name)
# time.sleep(1)
#
# # res=index(1,2,3) # wrapper(1,2,3)
# # print(res)
# #
# # res=home("egon")
# # print(res)
#
#
# # help(index)
# print(index.__name__)
# 例8:
def auth(func):
def wrapper(*args,**kwargs):
name=input("username>>: ").strip()
pwd=input("password>>: ").strip()
if name == "egon" and pwd == "123":
print('login successful')
res=func(*args,**kwargs)
return res
else:
print("username or password error")
return wrapper
@auth
def index():
print('from index')
index()