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Algorithm to return all combinations of k elements from n
...ickly, you'll have problems by 20 elements in your set -- 20C3 = 1140. And if you want to iterate over the set it's best to use a modified gray code algorithm so you aren't holding all of them in memory. These generate the next combination from the previous and avoid repetitions. There are many of t...
Test whether string is a valid integer
... trying to do something common enough: Parse user input in a shell script. If the user provided a valid integer, the script does one thing, and if not valid, it does something else. Trouble is, I haven't found an easy (and reasonably elegant) way of doing this - I don't want to have to pick it apart...
How to modify a text file?
...indicated, you can append to a file or overwrite part of it using seek but if you want to add stuff at the beginning or the middle, you'll have to rewrite it.
This is an operating system thing, not a Python thing. It is the same in all languages.
What I usually do is read from the file, make the m...
HttpServletRequest to complete URL
...URL().toString());
String queryString = request.getQueryString();
if (queryString == null) {
return requestURL.toString();
} else {
return requestURL.append('?').append(queryString).toString();
}
}
...
setting an environment variable in virtualenv
...
Very funny gif :D
– chachan
Nov 4 '14 at 22:47
3
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Postgis installation: type “geometry” does not exist
...
Thanks. BTW, If someone using 'psql' to run this code, make sure the role have 'Superuser' attribute/privilege.
– Yang
Dec 12 '15 at 3:09
...
Python json.loads shows ValueError: Extra data
...)
ValueError: Extra data: line 1 column 3 - line 1 column 5 (char 2 - 4)
If you want to dump multiple dictionaries, wrap them in a list, dump the list (instead of dumping dictionaries multiple times)
>>> dict1 = {}
>>> dict2 = {}
>>> json.dumps([dict1, dict2])
'[{}, {}]...
How to revert initial git commit?
...tial commit, but keeps all previously commited changes added to the index. If you want to also remove those changes, just execute a following git reset --hard. Even if incomplete, this answer is indeed the best one, so avoid using rm -fr .git (unless you know what you are doing).
...
How can you use an object's property in a double-quoted string?
...ll be replaced by that variable's value:
$foo = 2
"$foo"
becomes
"2"
If you don't want that you have to use single quotes:
$foo = 2
'$foo'
However, if you want to access properties, or use indexes on variables in a double-quoted string, you have to enclose that subexpression in $():
$foo =...
Comparing boxed Long values 127 and 128
I want to compare two Long objects values using if conditions. When these values are less than 128 , the if condition works properly, but when they are greater than or equal to 128 , comparison fails.
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