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When splitting an empty string in Python, why does split() return an empty list while split('\n') re
I am using split('\n') to get lines in one string, and found that ''.split() returns an empty list, [] , while ''.split('\n') returns [''] . Is there any specific reason for such a difference?
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Using Linq to get the last N elements of a collection?
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This approach preserves item order without a dependency on any sorting, and has broad compatibility across several LINQ providers.
It is important to take care not to call Skip with a negative number. Some providers, such as the Entity Framework, will produce an ArgumentException when presented ...
How to add an extra column to a NumPy array
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I think a more straightforward solution and faster to boot is to do the following:
import numpy as np
N = 10
a = np.random.rand(N,N)
b = np.zeros((N,N+1))
b[:,:-1] = a
And timings:
In [23]: N = 10
In [24]: a = np.random.rand(N,N)
In [25]: %timeit b = np.hstac...
Algorithm to get the excel-like column name of a number
I'm working on a script that generate some Excel documents and I need to convert a number into its column name equivalent. For example:
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How to insert a newline in front of a pattern?
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This works in bash and zsh, tested on Linux and OS X:
sed 's/regexp/\'$'\n/g'
In general, for $ followed by a string literal in single quotes bash performs C-style backslash substitution, e.g. $'\t' is translated to a literal tab. Plus, sed ...
Color text in terminal applications in UNIX [duplicate]
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printf(KMAG "magenta\n"); is much cleaner and faster than using %s.
– user142019
Feb 26 '11 at 12:43
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Get first n characters of a string
...hat's the fastest way to trim a string to a specific number of characters, and append '...' if needed?
19 Answers
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Why is pow(a, d, n) so much faster than a**d % n?
I was trying to implement a Miller-Rabin primality test , and was puzzled why it was taking so long (> 20 seconds) for midsize numbers (~7 digits). I eventually found the following line of code to be the source of the problem:
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Converting newline formatting from Mac to Windows
...In conclusion, simply replace every occurence of \n by \r\n.
Both unix2dos and dos2unix are not by default available on Mac OSX.
Fortunately, you can simply use Perl or sed to do the job:
sed -e 's/$/\r/' inputfile > outputfile # UNIX to DOS (adding CRs)
sed -e 's/\r$//' inputfil...
Why are elementwise additions much faster in separate loops than in a combined loop?
Suppose a1 , b1 , c1 , and d1 point to heap memory and my numerical code has the following core loop.
10 Answers
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