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Python: fastest way to create a list of n lists
...None, n)]
It does not have to create a new int object in every iteration and is about 15 % faster on my machine.
Edit: Using NumPy, you can avoid the Python loop using
d = numpy.empty((n, 0)).tolist()
but this is actually 2.5 times slower than the list comprehension.
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Difference between natural join and inner join
What is the difference between a natural join and an inner join?
11 Answers
11
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Random number from a range in a Bash Script
I need to generate a random port number between 2000-65000 from a shell script. The problem is $RANDOM is a 15-bit number, so I'm stuck!
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How do you get the logical xor of two variables in Python?
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Although this is clever and short, I'm not convinced it's clean. When someone reads this construct in the code, is it immediately obvious to them that this is an xor operation? I felt obliged to add a comment - a sign for me that I'm writing unclear...
Check if a file exists with wildcard in shell script [duplicate]
... completely silent.
EDIT: Since this answer has got a bit of attention (and very useful critic remarks as comments), here is an optimization that also relies on glob expansion, but avoids the use of ls:
for f in /path/to/your/files*; do
## Check if the glob gets expanded to existing files.
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Algorithm for creating a school timetable
...ble. Basically, it's about optimizing "hour-dispersion" (both in teachers and classes case) for given class-subject-teacher associations. We can assume that we have sets of classes, lesson subjects and teachers associated with each other at the input and that timetable should fit between 8AM and 4P...
What regular expression will match valid international phone numbers?
...rmat for matching a generic international phone number. I replaced the US land line centric international access code 011 with the standard international access code identifier of '+', making it mandatory. I also changed the minimum for the national number to at least one digit.
Note that if you en...
How to determine equality for two JavaScript objects?
...ortant to determine whether any two instances of MyClass are equal, only a and b are important. In some cases c might vary between instances and yet not be significant during comparison.
Note this issue applies when members may themselves also be instances of a type and these each would all be req...
How does one make random number between range for arc4random_uniform()?
so my goal in this codebit is to randomly roll two dice and as we all know your regular die only has 6 sides so I imported Foundation for access to arc4random_uniform(UInt32). I attempted using the range of (1..7) to avoid randomly getting 0 however that returned an error which I didn't enjoy too mu...
Automatically create an Enum based on values in a database lookup table?
How do I automatically create an enum and subsequently use its values in C# based on values in a database lookup table (using enterprise library data layer)?
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