您的if
声明确实不是做你认为它确实如此。
你申请运营商链接和正在测试两两件事:
(n == n[::-1]) and (n[::-1] is True)
这将始终是False
因为'0' is True
不True
。演示:
>>> n = str(0)
>>> n[::-1] == n is True
False
>>> n[::-1] == n
True
从comparisons documentation:
比较可以被任意链的,例如,x < y <= z
相当于x < y and y <= z
,不同之处在于y
只计算一次(但在这两种情况下z
不是在评价全部在x < y
被发现是错误的)。
你做不需要测试is True
这里; Python的if
说法是完全有能力测试,对自身的:
if n == n[::-1]:
你的下一个问题是,你永远不会改变n
,所以现在你会追加1000个'0'
字符串列表。
你会更好使用for
遍历xrange(1000)
并设置每次迭代n
:
def palin_generator():
"""Generates palindromic numbers."""
palindromes=[]
for count in xrange(10000):
n = str(count)
if n == n[::-1]:
palindromes.append(n)
print palindromes
现在你的函数的工作原理:
>>> palin_generator()
['0', '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', '202', '212', '222', '232', '242', '252', '262', '272', '282', '292', '303', '313', '323', '333', '343', '353', '363', '373', '383', '393', '404', '414', '424', '434', '444', '454', '464', '474', '484', '494', '505', '515', '525', '535', '545', '555', '565', '575', '585', '595', '606', '616', '626', '636', '646', '656', '666', '676', '686', '696', '707', '717', '727', '737', '747', '757', '767', '777', '787', '797', '808', '818', '828', '838', '848', '858', '868', '878', '888', '898', '909', '919', '929', '939', '949', '959', '969', '979', '989', '999', '1001', '1111', '1221', '1331', '1441', '1551', '1661', '1771', '1881', '1991', '2002', '2112', '2222', '2332', '2442', '2552', '2662', '2772', '2882', '2992', '3003', '3113', '3223', '3333', '3443', '3553', '3663', '3773', '3883', '3993', '4004', '4114', '4224', '4334', '4444', '4554', '4664', '4774', '4884', '4994', '5005', '5115', '5225', '5335', '5445', '5555', '5665', '5775', '5885', '5995', '6006', '6116', '6226', '6336', '6446', '6556', '6666', '6776', '6886', '6996', '7007', '7117', '7227', '7337', '7447', '7557', '7667', '7777', '7887', '7997', '8008', '8118', '8228', '8338', '8448', '8558', '8668', '8778', '8888', '8998', '9009', '9119', '9229', '9339', '9449', '9559', '9669', '9779', '9889', '9999']
很好的答案,谢谢你的回应。 – Chris