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How to count the frequency of the elements in an unordered list?
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Note: You should sort the list before using groupby.
You can use groupby from itertools package if the list is an ordered list.
a = [1,1,1,1,2,2,2,2,3,3,4,5,5]
from itertools import groupby
[len(list(group)) for key, group in groupby(a)]
Output:
[4, 4...
Is there a difference between using a dict literal and a dict constructor?
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I think you have pointed out the most obvious difference. Apart from that,
the first doesn't need to lookup dict which should make it a tiny bit faster
the second looks up dict in locals() and then globals() and the finds the builtin, so you can switch the beh...
Best way to represent a fraction in Java?
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It just so happens that I wrote a BigFraction class not too long ago, for Project Euler problems. It keeps a BigInteger numerator and denominator, so it'll never overflow. But it'll be a tad slow for a lot of operations that you know will never overflow.. a...
How to test if list element exists?
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This is actually a bit trickier than you'd think. Since a list can actually (with some effort) contain NULL elements, it might not be enough to check is.null(foo$a). A more stringent test might be to check that the name is actually defined in t...
Remove an item from a dictionary when its key is unknown
What is the best way to remove an item from a dictionary by value, i.e. when the item's key is unknown? Here's a simple approach:
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Find size of Git repository
... git 1.8.3 introduced a more efficient way to get a rough size: git count-objects -vH (see answer by @VonC)
For different ideas of "complete size" you could use:
git bundle create tmp.bundle --all
du -sh tmp.bundle
Close (but not exact:)
git gc
du -sh .git/
With the latter, you would also be...
How to convert a String to its equivalent LINQ Expression Tree?
This is a simplified version of the original problem.
7 Answers
7
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javascript i++ vs ++i [duplicate]
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The difference between i++ and ++i is the value of the expression.
The value i++ is the value of i before the increment. The value of ++i is the value of i after the increment.
Example:
var i = 42;
alert(i++); // shows 42
alert(i); // sh...
How do I concatenate strings in Swift?
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You can concatenate strings a number of ways:
let a = "Hello"
let b = "World"
let first = a + ", " + b
let second = "\(a), \(b)"
You could also do:
var c = "Hello"
c += ", World"
I'm sure there are more ways too.
Bit of description
let creates a con...
How and/or why is merging in Git better than in SVN?
I've heard in a few places that one of the main reasons why distributed version control systems shine, is much better merging than in traditional tools like SVN.
Is this actually due to inherent differences in how the two systems work, or do specific DVCS implementations like Git/Mercurial just ha...