大约有 14,200 项符合查询结果（耗时：0.0299秒） [XML]
Linq code to select one item
...
Depends how much you like the linq query syntax, you can use the extension methods directly like:
var item = Items.First(i => i.Id == 123);
And if you don't want to throw an error if the list is empty, use FirstOrDefault which returns the default value for the elem...
Java 8: Lambda-Streams, Filter by Method with Exception
I have a problem trying out the Lambda expressions of Java 8.
Usually it works fine, but now I have methods that throw IOException 's.
It's best if you look at the following code:
...
Can't find the PostgreSQL client library (libpq)
I'm trying to install PostgreSQL for Rails on Mac OS X 10.6. First I tried the MacPorts install but that didn't go well so I did the one-click DMG install. That seemed to work.
...
Pandas conditional creation of a series/dataframe column
...elect from:
df['color'] = np.where(df['Set']=='Z', 'green', 'red')
For example,
import pandas as pd
import numpy as np
df = pd.DataFrame({'Type':list('ABBC'), 'Set':list('ZZXY')})
df['color'] = np.where(df['Set']=='Z', 'green', 'red')
print(df)
yields
Set Type color
0 Z A green
1 ...
python: how to identify if a variable is an array or a scalar
...ad of list.
note: isinstance also supports a tuple of classes, check type(x) in (..., ...) should be avoided and is unnecessary.
You may also wanna check not isinstance(x, (str, unicode))
share
|
...
What are free monads?
... some time, but everyone just seems to use/discuss them without giving an explanation of what they are. So: what are free monads? (I'd say I'm familiar with monads and the Haskell basics, but have only a very rough knowledge of category theory.)
...
Relative frequencies / proportions with dplyr
...nt to calculate the proportion of different values within each group. For example, using the mtcars data, how do I calculate the relative frequency of number of gears by am (automatic/manual) in one go with dplyr ?
...
How do you make an array of structs in C?
...nt month;
int year;
}STUDENT;
int numStudents=3;
int x;
STUDENT* students = malloc(numStudents * sizeof *students);
for (x = 0; x < numStudents; x++){
students[x].firstName=(char*)malloc(sizeof(char*));
scanf("%s",students[x].firstName);
stude...
How to create “No Activate” form in Firemonkey
In XCode by adding these methods to your NSView subclass can prevent the window from becoming active when clicking on it:
2...
Are +0 and -0 the same?
... +0 = 0. However, in computing, some number representations allow for the existence of two zeros, often denoted by −0 (negative zero) and +0 (positive zero). This occurs in some signed number representations for integers, and in most floating point number representations. The number 0 is usually e...