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How to add column if not exists on PostgreSQL?
...D;
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You can't pass these as parameters, you'll need to do variable substitution in the string on the client side, but this is a self contained query that only emits a message if the column already exists, adds if it doesn't and will continue to fail on other errors (like an invalid data type).
I ...
How to convert list of tuples to multiple lists?
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From the python docs:
zip() in conjunction with the * operator can be used to unzip a list:
Specific example:
>>> zip((1,3,5),(2,4,6))
[(1, 2), (3, 4), (5, 6)]
>>> zip(*[(1, 2), (3, 4), (5, 6)])
[(1, 3, 5), (2, 4, 6)]
Or, if you really want lists...
Weird PHP error: 'Can't use function return value in write context'
I'm getting this error and I can't make head or tail of it.
12 Answers
12
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error LNK2019: 无法解析的外部符号_socket，该符号在函数 中被引用 - C/C+...
error LNK2019: 无法解析的外部符号_socket，该符号在函数 中被引用1>NetClient.obj : error LNK2019: 无法解析的外部符号 _closesocket@4，该符号在函数 _main 中被引用1>NetClient.obj : error L...1>NetClient.obj : error LNK2019: 无法解析的外部符号 _closesocket@...
How to change the name of a Django app?
I have changed the name of an app in Django by renaming its folder, imports and all its references (templates/indexes). But now I get this error when I try to run python manage.py runserver
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TypeError: Missing 1 required positional argument: 'self'
I am new to python and have hit a wall. I followed several tutorials but cant get past the error:
6 Answers
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How to implement the --verbose or -v option into a script?
... than putting the if in the function, which you might be tempted to do, do it like this:
if verbose:
def verboseprint(*args):
# Print each argument separately so caller doesn't need to
# stuff everything to be printed into a single string
for arg in args:
prin...
back button callback in navigationController in iOS
...hed a view onto the navigation controller and when I press the back button it goes to the previous view automatically. I want to do a few things when back button is pressed before popping the view off the stack. Which is the back button callback function?
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Javascript replace with reference to matched group?
... string, such as hello _there_ . I'd like to replace the two underscores with <div> and </div> respectively, using JavaScript . The output would (therefore) look like hello <div>there</div> . The string might contain multiple pairs of underscores.
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How to specify different Debug/Release output directories in QMake .pro file
...followed by make in whatever build directory you want to build in. So, run it once in a debug directory, once in a release directory.
That's how anyone building your project would expect it to work, and that's how Qt itself is set up to build, that's also how Qt Creator expects your .pro file to be...