Python3学习笔记1-1

# 迭代
def fact(n):
    if  n == 1:
        return 1
    return n * fact(n-1)
fact(1)
1

#
[x * x for x in range(1,11) if x % 2 == 0]
[4, 16, 36, 64, 100]
[m + n for m in 'abc' for n in 'xyz']
['ax', 'ay', 'az', 'bx', 'by', 'bz', 'cx', 'cy', 'cz']

＃首尾
a='    sadadas   '
print(a)
    sadadas   
print(a.strip())
sadadas

#Python内建的map()和reduce()函数
list(map(str, [1,2,4,4,5]))
['1', '2', '4', '4', '5']

from functools import reduce
def fn(x, y):
    return x * 10 + y
def char2num(s):
    digits = {'0':0, '1':1, '2':2, '3':3, '4':4}
    return digits[s]
reduce(fn, map(char2num, '1234'))
1234

from functools import reduce
digits = {'0':0, '1':1, '2':2, '3':3, '4':4}
def str2int(s):
    def fn(x, y):
        return x * 10 + y
    def charm2num(s):
        return digits[s]
    return reduce(fn, map(charm2num, s))
str2int('1234')
1234

from functools import reduce
digits = {'0':0, '1':1, '2':2, '3':3, '4':4}
def str2num(s):
    return digits[s]

def str2int(s):
    return reduce(lambda x, y: x * 10 + y, map(char2num, s))