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COUNT DISTINCT with CONDITIONS
I want to count the number of distinct items in a column subject to a certain condition, for example if the table is like this:
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Accessing the index in 'for' loops?
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Using an additional state variable, such as an index variable (which you would normally use in languages such as C or PHP), is considered non-pythonic.
The better option is to use the built-in function enumerate(), available in both Python 2 and 3:
for i...
How to read/write from/to file using Go?
I've been trying to learn Go on my own, but I've been stumped on trying read from and write to ordinary files.
8 Answers
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Fastest way to count exact number of rows in a very large table?
I have come across articles that state that SELECT COUNT(*) FROM TABLE_NAME will be slow when the table has lots of rows and lots of columns.
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Why do pthreads’ condition variable functions require a mutex?
I’m reading up on pthread.h ; the condition variable related functions (like pthread_cond_wait(3) ) require a mutex as an argument. Why? As far as I can tell, I’m going to be creating a mutex just to use as that argument? What is that mutex supposed to do?
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How do I get a class instance of generic type T?
...> . In a method of Foo , I want to get the class instance of type T , but I just can't call T.class .
21 Answers
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how to unit test file upload in django
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From Django docs on Client.post:
Submitting files is a special case. To POST a file, you need only
provide the file field name as a key, and a file handle to the file
you wish to upload as a value. For example:
c = Client()
with open('wishlist.doc') as f...
Expanding tuples into arguments
...tly what you request. The * operator simply unpacks the tuple (or any iterable) and passes them as the positional arguments to the function. Read more about unpacking arguments.
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Does Python have a string 'contains' substring method?
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You can use the in operator:
if "blah" not in somestring:
continue
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Using the HTML5 “required” attribute for a group of checkboxes?
When using the newer browsers that support HTML5 (FireFox 4 for example);
and a form field has the attribute required='required' ;
and the form field is empty/blank;
and the submit button is clicked;
the browsers detects that the "required" field is empty and does not submit the form; ins...