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private[this] vs private
...t very rich Java background I learnt to close everything (make it private) and open (provide accessors) if necessary. Scala introduces even more strict access modifier. Should I always use it by default? Or should I use it only in some specific cases where I need to explicitly restrict changing fiel...
How to throw an exception in C?
...tion (or other notification error form the CPU if there is)(How processor handles the case of division by zero).
Exceptions are defined in C++ and other languages though. Exception handling in C++ is specified in the C++ standard "S.15 Exception handling", there is no equivalent section in the C st...
What's the difference between dynamic (C# 4) and var?
...ing with C# v4, but I couldn't make out the difference between a "dynamic" and "var".
14 Answers
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Python unittest - opposite of assertRaises?
...r test must exit with a failure condition, not an error one. On the other hand, if in running the same code you would raise a KeyError, that would be an error, not a failure. In python - differently than some other languages - Exceptions are routinely used for control flow, this is why we have the e...
Django select only rows with duplicate field values
...ango. The problem is that this will return a ValuesQuerySet with only name and count. However, you can then use this to construct a regular QuerySet by feeding it back into another query:
dupes = Literal.objects.values('name')
.annotate(Count('id'))
.or...
How do I spool to a CSV formatted file using SQLPLUS?
...
Assuming that this is because you are executing a script and writing to a file, you should just "set termout off"
– BobC
Nov 2 '18 at 21:49
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How do I perform the SQL Join equivalent in MongoDB?
...t array field>
}
}
Of course Mongo is not a relational database, and the devs are being careful to recommend specific use cases for $lookup, but at least as of 3.2 doing join is now possible with MongoDB.
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Repeat string to certain length
...
def repeat_to_length(string_to_expand, length):
return (string_to_expand * ((length/len(string_to_expand))+1))[:length]
For python3:
def repeat_to_length(string_to_expand, length):
return (string_to_expand * (int(length/len(string_to_expand))+1))[:l...
How does Django's Meta class work?
...ciated database table name, whether the model is abstract or not, singular and plural versions of the name etc.
Short explanation is here: Django docs: Models: Meta options
List of available meta options is here: Django docs: Model Meta options
For latest version of Django: Django docs: Model Met...
Dynamic variable names in Bash
...
Use an associative array, with command names as keys.
# Requires bash 4, though
declare -A magic_variable=()
function grep_search() {
magic_variable[$1]=$( ls | tail -1 )
echo ${magic_variable[$1]}
}
If you can't use associative arrays (e.g., you m...