filter(func,itrable) 過濾
序列中的每個元素作為參數傳遞給函數進行判斷,傳回True或者False,最後将傳回True的元素放到新清單中
# eg: 奇數的判斷
def is_odd(n):
return n%2 == 1
templist = filter(is_odd,[1,2,3,4,5,6,7,8,9,10])
newlist = list(templist)
print(newlist)
map(func,itrable)
将傳入的函數依次作用到序列的每個元素,并把結果作為新的list傳回
def f(x):
return x*x
templist = map(f,[1,2,3,4,5,6])
newlist = list(templist)
print(newlist)
reduce(func,itrable[, initial])
函數會對參數序列中的元素進行累積,python3中,放置在functools子產品中
from functools import reduce
def add(x,y):
return x+y
res = reduce(add,[1,2,3,4,5])
res = reduce(lambda x,y:x+y,[1,2,3,4,5])
print(res)
# ex: 統計sentences = ['The Deep Learning textbook is a resource intended to help students and practitioners enter the field of machine learning in general and deep learning in particular.']中‘learning’出現的次數。
sentences = ['The Deep Learning textbook is a resource intended to help students and practitioners enter the field of machine learning in general and deep learning in particular.']
from functools import reduce
word_count = reduce(lambda a,x:a+x.count("learning"),sentences,0)
print(word_count)