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How do I get the object if it exists, or None if it does not exist?
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To make things easier, here is a snippet of the code I wrote, based on inputs from the wonderful replies here:
class MyManager(models.Manager):
def get_or_none(self, **kwargs):
try:
return self.get(**kwargs)
except ObjectDoesNotExist:
return...
How to squash commits in git after they have been pushed?
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Squash commits locally with
git rebase -i origin/master~4 master
and then force push with
git push origin +master
Difference between --force and +
From the documentation of git push:
Note that --force applies to all the refs that are pushed, hen...
Pandas: drop a level from a multi-level column index?
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Another way to do this is to reassign df based on a cross section of df, using the .xs method.
>>> df
a
b c
0 1 2
1 3 4
>>> df = df.xs('a', axis=1, drop_level=True)
# 'a' : key on which to get cross section
# axis=1 : ...
How to center canvas in html5
... bottom: 0;
left: 0;
right: 0;
}
The canvas will center itself based on the first parent element that has position set to relative or absolute, or the body if none is found.
Another approach would be to use display: flex, that is available in IE11
Also, make sure you use a recent docty...
SQL WHERE ID IN (id1, id2, …, idn)
...horrible performance-wise. It sends a query every loop and hammers the database with small queries. It also prevents it from using any optimizations for "value is one of those in a given list"
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JavaScript code to stop form submission
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Base on @Vikram Pudi answer, we can also do like this with pure Javascript
<form onsubmit="submitForm(event)">
<input type="text">
<input type="submit">
</form>
<script type="text/javascri...
“This project is incompatible with the current version of Visual Studio”
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VS 2012 has different project type support based on what you install at setup time and which edition you have. Certain options are available, e.g. web development tools, database development tools, etc. So if you're trying to open a web project but the web development...
Breaking out of nested loops [duplicate]
... of sentences and using several for loops to filter out specific sentences based on existence of specific words or numbers, before doing the actual work at the end of the outer for loop.
– Anthon
Oct 4 '12 at 6:51
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DatabaseError: current transaction is aborted, commands ignored until end of transaction block?
... prevent the error from occurring:
from django.db import transaction, DatabaseError
try:
a.save()
except DatabaseError:
transaction.rollback()
Refer : Django documentation
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improve...
php - get numeric index of associative array
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All solutions based on array_keys don't work for mixed arrays. Solution is simple:
echo array_search($needle,array_keys($haystack), true);
From php.net:
If the third parameter strict is set to TRUE then the array_search() function will ...