map&reduce
#map list输出 >>> map(str,[1,2,3,4]) ['1', '2', '3', '4']
#函数fn def fn(x,y): return x*10+y #函数char2num >>> def char2num(s): return{'0':88,'1':77,'2':66}[s] #reduce fn函数map char2num >>> reduce(fn,map(char2num,'012')) 9636
#过程:1.88,77,66 2.88*10+77=957 3.957*10+66=9636