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In a django model custom save() method, how should you identify a new object?
...
Updated: With the clarification that self._state is not a private instance variable, but named that way to avoid conflicts, checking self._state.adding is now the preferable way to check.
self.pk is None:
returns True within a new Model object, unless the object...
What is the difference between '/' and '//' when used for division?
...he 2.x line, there is no difference for integers unless you perform a from __future__ import division, which causes Python 2.x to adopt the 3.x behavior.
Regardless of the future import, 5.0 // 2 will return 2.0 since that's the floor division result of the operation.
You can find a detailed descr...
How do I call setattr() on the current module?
...
import sys
thismodule = sys.modules[__name__]
setattr(thismodule, name, value)
or, without using setattr (which breaks the letter of the question but satisfies the same practical purposes;-):
globals()[name] = value
Note: at module scope, the latter is eq...
How to create a DataTable in C# and how to add rows?
...e();
dt.Clear();
dt.Columns.Add("Name");
dt.Columns.Add("Marks");
DataRow _ravi = dt.NewRow();
_ravi["Name"] = "ravi";
_ravi["Marks"] = "500";
dt.Rows.Add(_ravi);
To see the structure, or rather I'd rephrase it as schema, you can export it to an XML file by doing the following.
To export only th...
Is there a way to make mv create the directory to be moved to if it doesn't exist?
... this one-liner (in bash):
mkdir --parents ./some/path/; mv yourfile.txt $_
Breaking that down:
mkdir --parents ./some/path
creates the directory (including all intermediate directories), after which:
mv yourfile.txt $_
moves the file to that directory ($_ expands to the last argument passe...
background function in Python
...
Do something like this:
def function_that_downloads(my_args):
# do some long download here
then inline, do something like this:
import threading
def my_inline_function(some_args):
# do some stuff
download_thread = threading.Thread(target=function_t...
How to check BLAS/LAPACK linkage in NumPy and SciPy?
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The method numpy.show_config() (or numpy.__config__.show()) outputs information about linkage gathered at build time. My output looks like this. I think it means I am using the BLAS/LAPACK that ships with Mac OS.
>>> import numpy as np...
Efficient way to apply multiple filters to pandas DataFrame or Series
...turn op(x[col],n)
In [15]: def f(x, *b):
return x[(np.logical_and(*b))]
In [16]: b1 = b(df, 'col1', ge, 1)
In [17]: b2 = b(df, 'col1', le, 1)
In [18]: f(df, b1, b2)
Out[18]:
col1 col2
1 1 11
Update: pandas 0.13 has a query method for these kind of use cases, assuming c...
Django: How do I add arbitrary html attributes to input fields on a form?
...ibutes. Here is some I used earlier to modify 3 fields: ``` for field_name in ['image', 'image_small', 'image_mobile']: field = self.fields.get(field_name) field.widget.attrs['data-file'] = 'file' ```
– Stuart Axon
Jun 6 '14 at 11:59
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Redirecting stdout to “nothing” in python
...eference to the original sys.stdout and set it back after. For example old_stdout = sys.stdout before any of the other code, then sys.stdout = old_stdout when you are done.
– Andrew Clark
Aug 20 '14 at 21:05
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