Ce matin, je prends qq minutes pour apprendre la fonction filter() de Python. Voici mes notes. Pour l'info, je suis ce tutorial de ce site:
https://www.liaoxuefeng.com/wiki/1016959663602400/1017404530360000
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和map()类似，filter()也接收一个函数和一个序列。和map()不同的是，filter()把传入的函数依次作用于每个元素，然后根据返回值是True还是False决定保留还是丢弃该元素。
### function used for filter() should return result of boolean type
def is_odd(n):
return n % 2 == 1
a = list(filter(is_odd, [1, 2, 4, 5, 6, 9, 10, 15]))
print(a) # 结果: [1, 5, 9, 15]
def not_empty(s):
return s and s.strip()
b = list(filter(not_empty, ['A', '', 'B', None, 'C', ' ']))
print(b) # 结果: ['A', 'B', 'C']
Voici un petit exemple pour tester.
## check if n is in format such like 121, 1331, 34543, 123321, etc...
def is_palindrome(n):
res = []
while True:
a = n % 10
n = n // 10
res.append(a)
if n == 0 :
break
l = len(res)
bool_res = True
for i in range(0, l//2):
bool_res = bool_res and (res[i] == res[l-i-1])
if not bool_res:
break
return bool_res
### 测试:
output = filter(is_palindrome, range(1, 1000))
print('1~1000:', list(output))
if list(filter(is_palindrome, range(1, 200))) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191]:
print('测试成功!')
else:
print('测试失败!')
Ce que j'ai eu de ce test:
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