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Selecting with complex criteria from pandas.DataFrame
...tup:
>>> import pandas as pd
>>> from random import randint
>>> df = pd.DataFrame({'A': [randint(1, 9) for x in range(10)],
'B': [randint(1, 9)*10 for x in range(10)],
'C': [randint(1, 9)*100 for x in range(10)]})
>>> df
A...
Should I use string.isEmpty() or “”.equals(string)?
...always wondering why others use this so often, but didn't take null values into account. Great :-)
– Peter Wippermann
Dec 2 '10 at 10:51
10
...
How to determine if binary tree is balanced?
... abs(Height(tree.left) - Height(tree.right)) <= 1)
Translating that into the programming language of your choice should be trivial.
Bonus exercise: this naive code sketch traverses the tree far too many times when computing the heights. Can you make it more efficient?
Super bonus exercise: ...
Task not serializable: java.io.NotSerializableException when calling function outside closure only o
...
RDDs extend the Serialisable interface, so this is not what's causing your task to fail. Now this doesn't mean that you can serialise an RDD with Spark and avoid NotSerializableException
Spark is a distributed computing engine and its main abstraction i...
Difference between shadowing and overriding in C#?
...
Well inheritance...
suppose you have this classes:
class A {
public int Foo(){ return 5;}
public virtual int Bar(){return 5;}
}
class B : A{
public new int Foo() { return 1;} //shadow
public override int Bar() {return 1;} //override
}
then when you call this:
A clA = new A();
...
ORDER BY the IN value list
...
You can do it quite easily with (introduced in PostgreSQL 8.2) VALUES (), ().
Syntax will be like this:
select c.*
from comments c
join (
values
(1,1),
(3,2),
(2,3),
(4,4)
) as x (id, ordering) on c.id = x.id
order by x.ordering
...
How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
... # "link back" if you need
You must also put a unique constraint on the foreign key column (addess.student_id) to prevent multiple rows in the child table (address) from relating to the same row in the referenced table (student).
One-to-many: Use a foreign key on the many side of the ...
Do I need quotes for strings in YAML?
...s values
I, however, use double-quotes for integer values that need to be converted to strings like:
docker-compose version like version: "3.8"
port numbers like "8080:8080"
However, for special cases like booleans, floats, integers, and other cases, where using double-quotes for the entry values...
What is the exact problem with multiple inheritance?
...people asking all the time whether multiple inheritance should be included into the next version of C# or Java. C++ folks, who are fortunate enough to have this ability, say that this is like giving someone a rope to eventually hang themselves.
...
Programmer Puzzle: Encoding a chess board state throughout a game
...ves”. The problem also says nothing about knowing the moves up to this point. That’s actually a problem as I’ll explain.
Castling
The game has proceeded as follows:
e4 e5
Nf3 Nc6
Bb5 a6
Ba4 Bc5
The board looks as follows:
White has the option of castling. Part of the requirements f...