python内置函数-range()+zip()+sorted()+map()+reduce()+filter()

'''
range(start,stop,step)
参数：
    start : 开始的值 ，默认值为0
    stop  ： 结束的值
    step： 可选，步进值 默认值为1
返回值： 可迭代的对象，数字序列
'''
#range函数的使用方式
# 只写一个参数，就是从零开始到10之前，9
 res = range(11)

# 两个参数时，第一个参数是开始的值，第二个参数是结束的值（在结束值之前）
 res = range(5,10)

# 三个参数， 参数1是开始值，参数2是结束值，参数三是步进值
 res = range(1,10,3)

# 获取一个倒叙的数字序列
 res = range(10,0,-1)
 res = range(10,0,-2)

res = range(-10,-20,-1)
res = range(-20,-10)
res = range(-10,10)
print(list(res))

# 获取range函数返回的数字序列的方法
 res = range(10)

 print(list(res))

 for i in res:
     print(i)

res = iter(res)
 print(next(res))
 print(next(res))

var1 = '1234'
var2 = ['a','b','c']
var3 = ('A','B','C','D')

res = zip(var1,var2,var3)
# print(res,type(res))

for i in res:
    print(i)
'''
('1', 'a', 'A')
('2', 'b', 'B')
('3', 'c', 'C')
('4', 'd', 'D')
'''

x = [1, 2, 3]
y = [4, 5, 6]
zipped = zip(x, y)
print(list(zipped))

print(zip(x, y)) # 迭代器对象，
print(*zip(x, y))# 组合好的多个元组数据

 获取一个数的绝对值
 print(abs(-99.99))

# 求和 从 start 开始自左向右对 iterable 中的项求和并返回总计值
 print(sum([1,2,3]))

# 获取最大值
 print(max([1,2,3]))
 print(max(99,12,45))

# 获取最小值
 print(min([2,1,6,-9]))
 print(min(6,7,1,0,-2))

# 幂运算  返回 x 的 y 次幂
 print(pow(2,3))

# 四舍五入
 r = round(3.1415926)
 r = round(3.1415926,2) # 小数点保留几位

 r = round(4.5) # 奇进偶退  1.5 = 2 2.5=2,3.5=4,4.5=4
 print(r)

# bin() 将数值类型转为二进制
print(bin(123)) # 0b1111011

# int() 将二进制转为整型
 print(int(0b1111011)) #1 23

# oct() 转为八进制数 01234567
 print(oct(123)) # 0o173

# hex() 转为十六进制数 0123456789abcdef
 print(hex(123)) # 0x7b

# 将字符转为 ascii
r = ord('a')
print(r)

# 将ascii转为字符
r = chr(65)
print(r)

arr = [3,7,1,-9,20,10]

 res = sorted(arr)  # [-9, 1, 3, 7, 10, 20]

 res = sorted(arr,reverse=True)  # [20, 10, 7, 3, 1, -9]

res = sorted(arr,key=abs)
 print(res)

 def func(num):
     print(num,num % 2)
     return num % 2

 arr = [3,2,4,6,5,7,9]

res = sorted(arr,key=func)
 print(res)

# 优化版
arr = [3,2,4,6,5,7,9]
res = sorted(arr,key=lambda x:x%2)
print(res)

# ['1','2','3','4']  # ==> [1,2,3,4]
# 普通的处理方法
 varlist = ['1','2','3','4']  # ==> [1,2,3,4]
 newlist = []
 for i in varlist:
     newlist.append(int(i))
 print(newlist)

 varlist = ['1','2','3','4']
 res = map(int,varlist) # <map object at 0x104ea8890>
 print(list(res))

 varlist = [1,2,3,4]
 newlist = []
 for i in varlist:
     res = i ** 2
     newlist.append(res)
 print(newlist)

varlist = [1,2,3,4]
 def myfunc(x):
     return x ** 2
 res = map(myfunc,varlist)
 print(res,list(res))

 res = map(lambda x:x**2,varlist)
 print(res,list(res))

from functools import reduce

varlist = [5,2,1,1]
res = ''
for i in varlist:
    res += str(i)
res = int(res)
print(res,type(res))
'''
5 2 1 1
5 * 10 + 2 == 52
52 * 10 + 1 == 521
521 * 10 + 1 == 5211
'''

def myfunc(x,y):
    return x*10+y
varlist = [5,2,1,1]

res = reduce(myfunc,varlist)
print(res,type(res))

def myfunc(s):
    vardict = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9}
    return vardict[s]

iter1 = map(myfunc,'456')

iter2 = reduce(lambda x,y:x*10+y,iter1)
print(iter2)

 newlist = []
 for i in varlist:
     if i % 2 == 0:
         newlist.append(i)
 print(newlist)

 def myfunc(n):
     if n % 2 == 0:
         return True
     else:
         return False

 it = filter(myfunc,varlist)
 print(it,list(it))

it = filter(lambda n:True if n % 2 == 0 else False,varlist)
print(it,list(it))