Python開發基礎 day5 函數的定義與使用
#coding:utf-8:
# x=‘你‘ # u‘hello‘
# print(x.encode(‘gbk‘))
# print(b‘\xc4\xe3‘)
# y=b‘\xc4\xe3‘
# print(y.decode(‘gbk‘))
# x=‘你‘ #unicode.encode(‘utf-8‘)
y=u‘你‘
print repr(y)
# while True:
# msg=input(‘>>: ‘)
#
# # print(len(msg))
# # res=len(msg)
# # if res < 5:
# # continue
# # else:break
#
#
# if len(msg) < 5:
# continue
# else:break
#
# with open(‘a.txt‘) as f:
# for i in f.readlines():
# print(i,end=‘‘)
# with open(‘a.txt‘) as f:
# for i in f:
# print(i,end=‘‘)
# with open(‘a.txt‘) as f:
# print(f.readline(),end=‘‘)
# print(f.readline(),end=‘‘)
# print(f.readline(),end =‘‘)
# print(f.readline(),end=‘‘)
# print(f.readline(), end=‘‘)
# print(f.readline(), end=‘‘)
# with open(‘a.txt‘,‘r‘,encoding=‘utf-8‘) as f:
# print(len(f.read()))
# with open(‘a.txt‘,‘rb‘) as f:
# file_size=len(f.read())
# import os
# print(os.path.getsize(‘a.txt‘))
函數參數的使用:
# def foo(x):
# print(x)
#
#
# foo( 1)
# foo(‘a‘)
# foo({‘a‘:2})
#形參與實參:
# def foo(x,y): #x=1,y=2
# return x+y
#
# foo(1,2)
#===================================part1
#位置參數:按照從左到右的順序依次定義的參數
def foo(x,y):
print(x)
print(y)
#按位置定義的形參,必須被傳值,多一個不行,少一個也不行
# foo(1,2,3)
#按位置定義的實參,與形參一一對應
# foo(2,10)
#===================================part2
#關鍵字參數:實參在定義時,按照key=value形式定義
# def foo(x,y):
# print(x)
# print(y)
#
# # foo(y=10,x=1)
# foo(y=10,x=1) #關鍵字參數可以不用像位置實參一樣與形參一一對應,指名道姓地傳值
def foo(x,y):
print(x)
print(y)
# foo(1,10)
# foo(x=1,y=10)
# foo(1,y=10)
# foo(y=10,1)
# foo(x=10,1)
# foo(1,x=10,y=20)
# def foo(x,y,z):
# print(x)
# print(y)
# print(z)
# # foo(1,z=20,10)
# foo(1,y=2,z=10)
#註意的問題一:位置實參必須在關鍵字實參的前面
#註意的問題二:實參的形式既可以用位置實參又可以是關鍵字實參,但是一個形參不能重復傳值
#===================================part3
#默認參數:在定義函數階段,就已經為形參賦值,定義階段有值,調用階段可以不用傳值
# def func(x,y=10):
# print(x)
# print(y)
# func(1,20)
# func(1)
# def func(y=10,x):
# print(x)
# print(y)
#位置實參
#關鍵字實參
#位置形參
#默認參數(形參)
#形參的應用:值經常變化的需要定義成位置形參,
# 值大多數情況下都一樣,需要定義成默認參數
# def register(name,age,sex=‘male‘):
# print(name,age,sex)
#
# register(‘alex‘,1000)
# register(‘wupeiqi‘,9000)
# register(‘yuanhao‘,10000)
# register(‘王鐵蛋‘,10000,‘female‘)
#默認參數需要註意的問題一:必須放在位置形參後面
#默認參數需要註意的問題二:默認參數通常要定義成不可變類型
#默認參數需要註意的問題三:默認參數只在定義階段被賦值一次
# x=10
# def func(name,age=x):
# print(name)
# print(age)
# x=20
#
# func(‘egon‘)
# def func(name,age=10,sex=‘male‘,hobby=[‘play1‘,‘play2‘]):
# print(name)
# print(age)
# print(hobby)
#
# func(‘egon‘)
#===================================part4
#可變長參數:可變長指的是實參的個數不固定
#按位置定義的可變長度的實參:*
#按關鍵字定義的可變長度的實參:**
#
# def func(x,y,*args): #x=1,y=2,args=(3,4,5,6)
# print(x,y)
# print(args)
#
# func(1,2,3,4,5,6)
# def func(x,y,*args): #args=(3,4,5,6)
# print(x,y)
# print(args)
#
# func(1,2,*(3,4,5,6)) #foo(1,2,3,4,5,6)
# def func(x,y,z):
# print(x,y,z)
#
# # func(1,*(2,3)) #func(1,2,3)
# func(*(2,3)) #func(2,3)
#
# def func(x,y=2,z=1):
# print(x,y,z)
#
#
# func(*(‘a‘,‘b‘,‘c‘)) #func(‘a‘,‘b‘,‘c‘)
# def func(x,y,**kwargs): #x=1,y=2,kwargs={‘a‘:1,‘b‘:3,‘z‘:3}
# print(x,y)
# print(kwargs)
#
# func(1,y=2,z=3,a=1,b=3)
# def func(x,y,**kwargs): #x=1,y=2,**kwargs=**{‘a‘:1,‘b‘:3,‘z‘:3}
# print(x,y)
# print(kwargs)
#
# func(1,y=2,**{‘a‘:1,‘b‘:3,‘z‘:3}) #func(1,y=2,z=3,b=3,a=1)
# def func(x,y=1,z=1):
# print(x,y,z)
#
# func(**{‘y‘:2,‘x‘:1,‘z‘:3}) #
# def wrapper(*args,**kwargs): #可以接受任意形式,任意長度的參數
# print(args)
# print(kwargs)
#
#
# wrapper(1,2,3,3,3,3,3,x=1,y=2,z=3)
#
# def index(name,group):
# print(‘welcome %s to index page,group is: %s‘ %(name,group))
#
# def wrapper(*args,**kwargs): #可以接受任意形式,任意長度的參數
# # print(args) #args=(1,2,3)
# # print(kwargs) #kwargs={‘x‘:1,‘y‘:2,‘z‘:3}
# index(*args,**kwargs) #index(*(1,2,3),**{‘x‘:1,‘y‘:2,‘z‘:3}) #index(1,2,3,z=3,y=2,x=1)
#
# wrapper(name=‘egon‘,group=‘group1‘)
#命名關鍵字參數:定義在*後的形參,這類形參,必須被傳值,而且要求實參必須是以關鍵字的形式來傳值
# def register(**kwargs):
# print(kwargs)
# if ‘name‘ in kwargs:
# print(kwargs[‘name‘])
# if ‘age‘ in kwargs:
# print(kwargs[‘age‘])
#
#
# # register(name=‘egon‘,age=18)
# register()
# def register(*args,name=‘egon‘,age):
# print(args)
# print(name)
# print(age)
#
# # register(name=‘egon‘,age=18)
# register(1,2,2,3,age=10)
#
# def register(name,age,*,group,**kwargs):
# print(name)
# print(age)
# print(kwargs)
#
#
# # register(‘egon‘,18)
# register(‘egon1‘,18,hobby=‘paly1‘,group=‘group1‘)
# def func(x,y=1,*args,z,**kwargs):
# print(x)
# print(y)
# print(args)
# print(z)
# print(kwargs)
#
# func(1,2,3,4,5,z=10,a=1,b=2)
#
# def func(x,*args,z=1,**kwargs):
# print(x)
# print(args)
# print(z)
# print(kwargs)
#
# func(1,2,3,4,5,a=1,b=2,c=3)
#形參:位置形參,默認參數,*args,命名關鍵字參數,**kwargs
函數的返回值:
# y=x**2
# def func(x):
# return x**2
# y=func(10) # 10**2
#
# print(y)
# def foo():
# return None
#
# res=foo()
# print(res)
# def foo():
# return {‘a‘:1}
#
# res=foo()
# print(res[‘a‘])
# def foo():
# return {‘a‘:1},1,‘a‘,[1,2]
#
# res=foo()
# print(res)
‘‘‘
返回值:可以返回任意類型
沒有return:None
return value: value
return val1,val2,val3 :(val1,val2,val3)
return的效果:只能返回一次值,終止函數的執行
‘‘‘
def foo():
return 1
print(‘=====>‘)
return 2
return 3
return 4
print(foo())
函數的使用原則:
#函數的使用必須遵循:先定義後使用的原則
#函數的定義,與變量的定義是相似的,如果沒有事先定義函數而直接引用
#就相當於在引用一個不存在變量名
# print(x) #NameError
# x=1
# func
#
# def func():
# print(‘hello world‘)
# def func():
# print(‘hello world‘)
#
# # print(func)
# func()
# def bar():
# print(‘from bar‘)
#
# def foo():
# print(‘from foo‘)
# bar()
#
# foo()
# #定義階段
# def foo():
# print(‘from foo‘)
# bar()
#
# def bar():
# print(‘from bar‘)
#
# #調用階段
# foo()
#定義階段:只檢測語法,不執行代碼
# def func():
# if 1>2
# print(‘hahahahahahah‘)
def func(): #語法沒問題,邏輯有問題,引用一個不存在的變量名
asdfasdfasdfasdfasdf
函數對象:
#函數是第一類對象: 指的是函數可以被當做數據傳遞
def func():
print(‘from func‘)
#可被引用
# f=func
#可以當做函數的參數
# def func():
# print(‘from func‘)
# def foo(x):
# print(x)
# x()
#
# foo(func)
#可以當做函數的返回值
# def foo():
# print(‘from foo‘)
# def bar():
# return foo
# f=bar()
# print(f)
# print(foo)
# x=0
# def f1():
# x=1
# def f2():
# # x=2
# print(x)
# return f2
# f=f1()
# # print(f)
# f()
#可以當做容器類型的元素
# def select():
# print(‘select function‘)
#
# func_dic={
# ‘select‘:select,
# }
#
# # print(func_dic[‘select‘])
# func_dic[‘select‘]()
#
# def select():
# print(‘select func‘)
#
# def delete():
# print(‘delete func‘)
#
# def change():
# print(‘change func‘)
#
# def add():
# print(‘add func‘)
#
#
# while 1:
# cmd=input(‘>>: ‘).strip()
# if not cmd:continue
# if cmd == ‘select‘:
# select()
# elif cmd == ‘delete‘:
# delete()
# elif cmd == ‘change‘:
# change()
# elif cmd == ‘add‘:
# add()
# else:
# print(‘無效的命令‘)
def select(cmd_l):
filename=cmd_l[-1]
pattern=cmd_l[1]
with open(filename,‘r‘,encoding=‘utf-8‘) as f:
for line in f:
if pattern in line:
print(line)
def delete():
print(‘delete func‘)
def change():
print(‘change func‘)
def add():
print(‘add func‘)
def check():
print(‘check func‘)
func_dic={
‘select‘:select,
‘delete‘:delete,
‘change‘:change,
‘add‘:add,
‘check‘:check,
}
while 1:
inp=input(‘>>: ‘).strip()
if not inp:continue
cmd_l=inp.split()
# print(cmd_l)
cmd=cmd_l[0]
if cmd in func_dic:
func_dic[cmd](cmd_l)
else:
print(‘無效的命令‘)
函數嵌套:
#函數的嵌套調用
#
# def max2(x,y):
# if x > y:
# return x
# else:
# return y
#
# def max4(a,b,c,d):
# res1=max2(a,b) #23
# res2=max2(res1,c) #23
# res3=max2(res2,d) #31
# return res3
#
#
# print(max4(11,23,-7,31))
#函數的嵌套定義
def f1():
def f2():
def f3():
print(‘from f3‘)
print(‘from f2‘)
f3()
print(‘from f1‘)
f2()
# print(f1)
f1()
‘‘‘
from f1
from f2
from f3
‘‘‘
名稱空間與作用域:
#名字空間:存放名字與值的綁定關系
#名稱空間分為三種
#內置名稱空間:python解釋器自帶的名字,python解釋器啟動就會生成
#全局名稱空間:文件級別定義的名字都會存放與全局名稱空間,執行python文件時會產生
# x=1
# def func():
# pass
#
# class Foo:
# pass
#
# import os
#
# if 1 > 2 :
# y=3
#局部名稱空間:定義在函數內部的名字,局部名稱空間只有在調用函數時才會生效,函數調用結束則失效
# def func(x,y): #x=1,y=2
# z=3
# func(1,2)
#三者的加載順序:內置名稱空間->全局名稱空間->局部名稱空間
#取值:局部名稱空間->全局名稱空間->內置名稱空間
# # max=10
# def func(): #x=1
# # max=20
# print(max)
#
#
# func()
# max=10
#
# def func(): #x=1
# max=20
# # print(max)
# func()
#
#
# print(max)
#
# # x=0
# def f1():
# # x=1
# def f2():
# # x=2
# def f3():
# # x=3
# print(x)
# f3()
# f2()
#
# f1()
#作用域:作用範圍
#全局作用域:內置名稱空間與全局名稱空間的名字屬於全局範圍,
# 在整個文件的任意位置都能被引用,全局有效
#局部作用域:局部名稱空間的名字屬於局部範圍,
#只在函數內部可以被引用,局部有效
# x=1
# def foo():
# def f2():
# print(x)
# f2()
# def bar():
# print(x)
#
# foo()
# bar()
# def f1():
# x=1
# def f2(): #f2=value
# # x=2
# print(x)
# f2()
# f1()
x=1
def func():
x=2
def f1():pass
# print(dir(globals()[‘__builtins__‘])) #全局作用域name
# print(locals()) #局部作用域name
func()
print(globals() is locals())
#局部作用域----->全局作用域
Python開發基礎 day5 函數的定義與使用