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Python: fastest way to create a list of n lists
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The probably only way which is marginally faster than
d = [[] for x in xrange(n)]
is
from itertools import repeat
d = [[] for i in repeat(None, n)]
It does not have to create a new int object in every iteration and is about 15 % faster on my machine.
Edi...
Android: upgrading DB version and adding new table
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1. About onCreate() and onUpgrade()
onCreate(..) is called whenever the app is freshly installed. onUpgrade is called whenever the app is upgraded and launched and the database version is not the same.
2. Incrementing the db version
You need a constructor like:
MyOpenHelp...
Object reference not set to an instance of an object.Why doesn't .NET show which object is `null`?
...ull
IL_0002: stloc.0 // s
IL_0003: ldloc.0 // s
IL_0004: callvirt System.String.get_Length
IL_0009: call System.Console.WriteLine
It is the callvirt opcode that throws the NullReferenceException and it does that when the first argument on the evaluation stack is a null ...
Sort Go map values by keys
...tween runs of the program. In practice, not only is it undefined, it's actually intentionally randomized. This is because it used to be predictable, and the Go language developers didn't want people relying on unspecified behavior, so they intentionally randomized it so that relying on this behavior...
In Python, how does one catch warnings as if they were exceptions?
...ationWarning)
with warnings.catch_warnings(record=True) as w:
# Cause all warnings to always be triggered.
warnings.simplefilter("always")
# Trigger a warning.
fxn()
# Verify some things
assert len(w) == 1
assert issubclass(w[-1].category, DeprecationWarning)
assert ...
Using getopts to process long and short command line options
...or using the bash builtin getopts to mimic long options. That solution actually makes a short option whose character is "-". So you get "--" as the flag. Then anything following that becomes OPTARG, and you test the OPTARG with a nested case.
This is clever, but it comes with caveats:
getopts ca...
How to output only captured groups with sed?
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Ask your sysadmin to install gsed. You'd be amazed at what a few donuts will get you...
– avgvstvs
Dec 11 '12 at 13:08
3
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How do I create a new class in IntelliJ without using the mouse?
...rything is possible with keyboard only with the debugger. CrazyCoder, i challenge you to unplug your keyboard and work with IntelliJ!!!
– JavaRocky
Feb 12 '10 at 4:31
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Updating MySQL primary key
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11
If the primary key happens to be an auto_increment value, you have to remove the auto increment...
Django Setup Default Logging
...can't seem to figure out how to setup a "default" logger for my Django installation. I would like to use Django 1.3's new LOGGING setting in settings.py .
...