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python design patterns [closed]
...nd the primitive Null value.
This object just eats the lack of attribute error, and you can avoid checking for their existence.
It's nothing more than
class Null(object):
def __init__(self, *args, **kwargs):
"Ignore parameters."
return None
def __call__(self, *args, **k...
How to verify if a file exists in a batch file?
...hat the /c /d /h /e /i /y means:
/C Continues copying even if errors occur.
/D:m-d-y Copies files changed on or after the specified date.
If no date is given, copies only those files whose
source time is newer than the destination time.
/H ...
PostgreSQL Crosstab Query
...
This does not work for me, for postgresql. I get the error ERROR: 42803: aggregate function calls may not be nested
– Audrey
Nov 12 '14 at 12:05
1
...
memory_get_peak_usage() with “real usage”
...031 MiB
real: 1 MiB
not real: 0.97883605957031 MiB
real: 1 MiB
PHP Fatal error: Allowed memory size of 1048576 bytes exhausted (tried to allocate 793601 bytes) in /home/niko/test.php on line 7
Seems like real usage is the memory allocated from the system - which seems to get allocated in larger...
Django migration strategy for renaming a model and relationship fields
...ions.RenameField('YetAnotherModel', 'foo', 'bar')
]
You may get some errors if you don't update the names where it's imported e.g. admin.py and even older migration files (!).
Update: As ceasaro mentions, newer versions of Django are usually able to detect and ask if a model is renamed. So tr...
Android adb “Unable to open sync connection!”
...files" issue. I manually tried to install the app when getting the "sync" error above and that's when I got the "too many open files" clue. one brute workaround, based on some old posts, seems to be to restart the phone, and one google engineer suggested doing it twice, the second time before it g...
How to calculate the running time of my program? [duplicate]
...s in the main method, calendar will be defined two times -> compilation error
– krtek
Mar 5 '11 at 13:35
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Set margins in a LinearLayout programmatically
...ckage android.widget.RelativeLayout.LayoutParams, or else there will be an error.
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java.util.Date to XMLGregorianCalendar
...d for producing dates and times in XML format for XML documents. Like 2009-05-07T19:05:45.678+02:00 or 2009-05-07T17:05:45.678Z. These formats agree well enough with ISO 8601 that the classes of java.time, the modern Java date and time API, can produce them, which we prefer.
No conversion necessar...
Python 2.7 getting user input and manipulating as string without quotations
...ter a number: ")) #integer input
If you enter a string for int cast ValueError: invalid literal for int() with base 10:
x = float(input("Enter a float number: ")) #float input
If you enter a string for float cast ValueError: could not convert string to float
x = eval(input("Enter a float numbe...