Python基础篇 第六节课
作用域
name = "alex" def foo(): name = "KLY" def bar(): print(name) bar() foo() #输出KLY
name = "alex" def foo(): # name = "KLY" def bar(): print(name) bar() foo() #输出alex
name = "alex" def foo(): name = "KLY" def bar(): print(name) return bar a = foo() print(a) a() #输出KLY
def test1(): print("in the test1") def test(): print("in the test") return test1() res = test() print(res) #输出 in the test in the test1 None
def foo(): name = "KLY" def bar(): name = "JZH" def tt(): print(name) return tt return bar # bar = foo() # tt = bar() # print(tt) # tt() foo()()() #输出JZH
匿名函数
def c(x): return x+1 a = c(10) print(a) func = lambda x:x+1 print(func(10)) #输出11
name = "LJH" def change_name(x): return name + "_sb" res = change_name(name) print(res) f = lambda x:x+"_sb" res = f(name) print(res) #输出 LJH_sb LJH_sb
func = lambda x,y,z:x+y+z print(func(1,2,3)) #输出6
f = lambda x,y,z:(x+1,y+1,z+1) print(f(1,2,3)) #输出(2, 3, 4)
函数式编程
把函数当做参数传给另一个函数
def foo(n): print(n) def bar(name): print("my name is %s" %name) foo(bar("LJH")) def bar(): print("from bar") def foo(): print("from foo") return bar n = foo() n() def hanle(): print("from handle") return hanle n = hanle() n() #输出 my name is LJH None from foo from bar from handle from handle
尾调用
最后一步调用函数
def foo(x): x += 1 return x def a(): return foo(6)
map函数
num_1 = [2,4,6,8,5,9] def map_test(array): ret=[] for i in array: ret.append(i**2) return ret ret = map_test(num_1) print(ret) #输出[4, 16, 36, 64, 25, 81]
num_1 = [2,4,6,8,5,9] def add_one(x): #lambda x:x+1 return x+1 def reduce(x): #lambda x:x-1 return x-1 def pf (x): #lambda x:x**2 return x**2 def map_test(func,array): ret = [] for i in num_1: res = func(i) ret.append(res) return ret print(map_test(add_one,num_1)) #print(map_test(lambda x:x+1,num_1)) print(map_test(reduce,num_1)) #print(map_test(lambda x:x-1,num_1)) print(map_test(pf,num_1)) #print(map_test(lambda x:x**2,num_1)) #输出 [3, 5, 7, 9, 6, 10] [1, 3, 5, 7, 4, 8] [4, 16, 36, 64, 25, 81]
num_1 = [2,4,6,8,5,9] def map_test(func,array): ret = [] for i in array: res = func(i) ret.append(res) return ret print(map_test(lambda x:x+1,num_1)) print(list(map_test(lambda x:x+1,num_1))) #输出 [3, 5, 7, 9, 6, 10] [3, 5, 7, 9, 6, 10]
num_1 = [2,4,6,8,5,9] # def map_test(func,array): # ret = [] # for i in array: # res = func(i) # ret.append(res) # return ret # print(map_test(lambda x:x+1,num_1)) # print(list(map_test(lambda x:x+1,num_1)) print(list(map(lambda x:x+1,num_1))) #输出[3, 5, 7, 9, 6, 10]
msg = "konglingyueshishuaige" print(list(map(lambda x:x.upper(),msg))) #输出 ['K', 'O', 'N', 'G', 'L', 'I', 'N', 'G', 'Y', 'U', 'E', 'S', 'H', 'I', 'S', 'H', 'U', 'A', 'I', 'G', 'E']
filter函数
Moive_people = {"SB_JZJ","SB_HJHJ","SB_JKDH","KLY"}
ret = []
for i in Moive_people:
if not i .startswith("SB"):
ret.append(i)
print(ret)
#输出['KLY']
Moive_people = {"SB_JZJ","SB_HJHJ","SB_JKDH","KLY"}
def filter_test(array):
ret = []
for i in array:
if not i .startswith("SB"):
ret.append(i)
return ret
res = filter_test(Moive_people)
print(res)
#输出['KLY']
oive_people = {"SB_JZJ_SB","SB_HJHJ_SB","SB_JKDH_SB","KLY"}
def sb_show(n): #lambda n:n.endswith("SB")
return n.endswith("SB")
def filter_test(func,array):
ret=[]
for i in array:
if not func(i):
ret.append(i)
return ret
res = filter_test(sb_show,Moive_people) #res = filter_test(lambda n:n.endswith("SB"),Movie_people)
print(res) #print(res)
#输出['KLY']
Moive_people = {"SB_JZJ_SB","SB_HJHJ_SB","SB_JKDH_SB","KLY"}
# def sb_show(n):
# return n.endswith("SB")
# def filter_test(func,array):
# ret=[]
# for i in array:
# if not func(i):
# ret.append(i)
# return ret
#
# res = filter_test(sb_show,Moive_people)
# print(res)
print(list(filter(lambda n:not n.endswith("SB"),Moive_people)))
#输出['KLY']
reduce 函数
res = 0 num_1 = [1,3,5,698,5] for num in num_1: res +=num print(res) #输出712
a = [1,5,6,486,444] def reduce_test(array): res = 0 for num in array: res +=num return res print(reduce_test(a)) #输出942
a = [1,5,52,486,444] def reduce_test(func,array): res = array.pop(0) for num in array: res = func(res,num) return res print(reduce_test(lambda x,y:x*y,a)) #输出56103840
a = [1,5,52,486,444] def reduce_test(func,array,init= None): if init is None: res = array.pop(0) else: res = init for num in array: res = func(res,num) return res print(reduce_test(lambda x,y:x*y,a,1)) #输出 56103840
from functools import reduce a = [1,5,52,486,444] print(reduce(lambda x,y:x+y,a,2)) #输出990
小结：
map 处理序列中的乜咯元素，得到的结果是一个列表，该列表元素及位置与原来的一样
filter 遍历序列中的每个元素，判断每个元素得到的布尔值，如果是True则留下
reduce 处理一个序列，然后把序列进行合并操作
内置函数
# print(abs(-456)) #绝对值 # print(all([1,2,"1"]) #判断有无空值，有则False # # name = "你好" # print(bytes(name,encoding = "utf-8")) # print(bytes(name,encoding = "utf-8").decode("utf-8")) # print(bool("")) #判断布尔值，0 None，空都为False # print(bin(12)) #把十进制转为二进制 # print(hex(45)) #把十进制转为十六进制 # print(oct(456)) #把十进制转为八进制 # print(chr(45)) #转化为一个值 # print(divmod(10,3)) #取商留余 # dic = {"name":"alex"} # dic_str = str(dic) # dic_str # eval(dic_str) # d1 =eval(dic_str) # print(d1["name"] ) #把字符串中的数据结构提取出来 # express = "1+2*(3/3-1)-2" # print(eval(express)) #把字符串中的表达式进行运算 # print(hash("541515dsds215")) # hash特征 长度固定 不能根据hash的值反推出字符串 在一个程序中，只要变量不变，hash值不会改变 # print(isinstance("abc",str)) #判断前一个变量是否为后一个类型 # print(globals()) #全局变量 # print(locals()) #局部变量 # l = [1,3,100,-120,566] # print(max(l)) #取最大值 # print(min*(l)) #取最小值
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