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Accessing class variables from a list comprehension in the class definition
...owing will fail:
class A:
a = 42
b = list(a + i for i in range(10))
So, to summarize: you cannot access the class scope from functions, list comprehensions or generator expressions enclosed in that scope; they act as if that scope does not exist. In Python 2, list comprehensions were i...
Adding 'serial' to existing column in Postgres
I have a small table (~30 rows) in my Postgres 9.0 database with an integer ID field (the primary key) which currently contains unique sequential integers starting at 1, but which was not created using the 'serial' keyword.
...
promise already under evaluation: recursive default argument reference or earlier problems?
...g the two instances where they occur we get:
f <- function(x, T) {
10 * sin(0.3 * x) * sin(1.3 * x^2) + 0.001 * x^3 + 0.2 * x + 80
}
g <- function(x, T, f. = f) { ## 1. note f.
exp(-f.(x)/T)
}
test<- function(g. = g, T = 1) { ## 2. note g.
g.(1,T)
}
test()
## [1] 8.560335e...
Convert a float64 to an int in Go
...to an int truncates the float, which if your system internally represent 2.0 as 1.9999999999, you will not get what you expect. The various printf conversions deal with this and properly round the number when converting. So to get a more accurate value, the conversion is even more complicated than...
How to access pandas groupby dataframe by key
...group method:
In [21]: gb.get_group('foo')
Out[21]:
A B C
0 foo 1.624345 5
2 foo -0.528172 11
4 foo 0.865408 14
Note: This doesn't require creating an intermediary dictionary / copy of every subdataframe for every group, so will be much more memory-efficient that creating...
What is the default value for enum variable?
...
It is whatever member of the enumeration represents the value 0. Specifically, from the documentation:
The default value of an enum E is the value produced by the expression (E)0.
As an example, take the following enum:
enum E
{
Foo, Bar, Baz, Quux
}
Without overriding the ...
Export database schema into SQL file
Is it possible in MS SQL Server 2008 to export database structure into a T-SQL file?
4 Answers
...
Making heatmap from pandas DataFrame
...5, 4)), index=index, columns=columns)
plt.pcolor(df)
plt.yticks(np.arange(0.5, len(df.index), 1), df.index)
plt.xticks(np.arange(0.5, len(df.columns), 1), df.columns)
plt.show()
This gives:
share
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...
Why is using “for…in” for array iteration a bad idea?
...5; // Perfectly legal JavaScript that resizes the array.
for (var i = 0; i < a.length; i++) {
// Iterate over numeric indexes from 0 to 5, as everyone expects.
console.log(a[i]);
}
/* Will display:
undefined
undefined
undefined
undefined
undefined
5
*/
...