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string sanitizer for filename

...a whitelist of characters you are happy to be used? For example, you could allow just good ol' a-z, 0-9, _, and a single instance of a period (.). That's obviously more limiting than most filesystems, but should keep you safe. ...
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Fastest way to get the first object from a queryset in django?

...eturn None if there aren't any. There are lots of ways to do this which all work. But I'm wondering which is the most performant. ...
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Will the base class constructor be automatically called?

... age of customer be 2? It seems like the base class's constructor will be called no matter what. If so, why do we need to call base at the end sometimes? ...
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namedtuple and default values for optional keyword arguments

...lds) >>> Node() Node(val=None, left=None, right=None) Order In all versions of Python, if you set fewer default values than exist in the namedtuple, the defaults are applied to the rightmost parameters. This allows you to keep some arguments as required arguments. >>> Node.__ne...
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How do I find where an exception was thrown in C++?

I have a program that throws an uncaught exception somewhere. All I get is a report of an exception being thrown, and no information as to where it was thrown. It seems illogical for a program compiled to contain debug symbols not to notify me of where in my code an exception was generated. ...
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Django: How to completely uninstall a Django app?

What is the procedure for completely uninstalling a Django app, complete with database removal? 5 Answers ...
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Determining Referer in PHP

...s the most reliable and secure way to determine what page either sent, or called (via AJAX), the current page. I don't want to use the $_SERVER['HTTP_REFERER'] , because of the (lack of) reliability, and I need the page being called to only come from requests originating on my site. Edit: I am...
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Complete Working Sample of the Gmail Three-Fragment Animation Scenario?

...at I'll refer to as "the Gmail three-fragment animation" scenario. Specifically, we want to start with two fragments, like this: ...
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Principal component analysis in Python

... Months later, here's a small class PCA, and a picture: #!/usr/bin/env python """ a small class for Principal Component Analysis Usage: p = PCA( A, fraction=0.90 ) In: A: an array of e.g. 1000 observations x 20 variables, 1000 rows x 20 colum...
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One-liner to check whether an iterator yields at least one element?

... Similarly if you need to check if the iterator is empty, one could use all(False for _ in iterator) will check if the iterator is empty. (all returns True if the iterator is empty, otherwise it stops when it sees the first False element) – KGardevoir Apr 3 ...