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What is a mixin, and why are they useful?

... and `==`, but this class does NOT implement those methods.""" def __ne__(self, other): return not (self == other) def __lt__(self, other): return self <= other and (self != other) def __gt__(self, other): return not self <= other def __ge__(self, ot...
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【解决】scrapyd启动job时报错:exceptions.TypeError: __init__() got an ...

【解决】scrapyd启动job时报错:exceptions.TypeError: __init__() got an unexpected keyword argument '_job'进入项目spiders目录, 修改 spider py 文件(你自己的spider的主文件):def __init__(self):改为:def __init__(self, *args, **kwargs):最后不要忘了重新部署一...
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Difference between a theta join, equijoin and natural join

... yourself). ** I don't quite know what the result of SELECT * FROM table_expression; is. I know it is not a relation because, among other reasons, it can have columns with duplicate names or a column with no name. I know it is not a set because, among other reasons, the column order is significan...
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How do I get the number of elements in a list?

...objects with a "size" in Python, in particular, have an attribute called ob_size, where the number of elements in the object is cached. So checking the number of objects in a list is very fast. But if you're checking if list size is zero or not, don't use len - instead, put the list in a boolean co...
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How to access outer class from an inner class?

...f): return Outer.Inner(self) class Inner(object): def __init__(self, outer_instance): self.outer_instance = outer_instance self.outer_instance.somemethod() def inner_method(self): self.outer_instance.anothermethod() ...
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How to read a single character from the user?

...Windows, Linux and OSX: http://code.activestate.com/recipes/134892/ class _Getch: """Gets a single character from standard input. Does not echo to the screen.""" def __init__(self): try: self.impl = _GetchWindows() except ImportError: self.impl = _Ge...
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Are nested try/except blocks in python a good programming practice?

...EAFP. Personally, I prefer to avoid nesting when it's not necessary: def __getattribute__(self, item): try: return object.__getattribute__(item) except AttributeError: pass # fallback to dict try: return self.dict[item] except KeyError: raise Attrib...
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How do I protect Python code? [closed]

... Ned BatchelderNed Batchelder 306k6464 gold badges503503 silver badges608608 bronze badges ...
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Convert HTML + CSS to PDF [closed]

...| edited Aug 25 '16 at 12:06 community wiki 5 r...
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How to parse a date? [duplicate]

... @jwl how to parce Sun Dec 06 11:15:00 IST 2015 this date – Sagar Dec 11 '18 at 9:21 ...