大约有 48,000 项符合查询结果（耗时：0.0525秒） [XML]
How to convert a data frame column to numeric type?
...
18 Answers
18
Active
...
How to reorder data.table columns (without copying)
...
185
Use setcolorder():
library(data.table)
x <- data.table(a = 1:3, b = 3:1, c = runif(3))
x
#...
How to count the number of true elements in a NumPy bool array
...:
>>> import numpy as np
>>> boolarr = np.array([[0, 0, 1], [1, 0, 1], [1, 0, 1]], dtype=np.bool)
>>> boolarr
array([[False, False, True],
[ True, False, True],
[ True, False, True]], dtype=bool)
>>> np.sum(boolarr)
5
Of course, that is a bool...
How to add new item to hash
...
Create the hash:
hash = {:item1 => 1}
Add a new item to it:
hash[:item2] = 2
share
|
improve this answer
|
follow
...
SQL query return data from multiple tables
...
Part 1 - Joins and Unions
This answer covers:
Part 1
Joining two or more tables using an inner join (See the wikipedia entry for additional info)
How to use a union query
Left and Right Outer Joins (this stackOverflow answer ...
Syntax for creating a two-dimensional array
...
12 Answers
12
Active
...
Python integer division yields float
...
answered Aug 15 '09 at 21:51
Brandon E TaylorBrandon E Taylor
23.1k66 gold badges4343 silver badges6868 bronze badges
...
Selecting with complex criteria from pandas.DataFrame
...; 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 B C
0 9 40 300
1 9 70 700
2 5 70 90...
How to filter a dictionary according to an arbitrary condition function?
... comprehension:
{k: v for k, v in points.iteritems() if v[0] < 5 and v[1] < 5}
And in Python 3:
{k: v for k, v in points.items() if v[0] < 5 and v[1] < 5}
share
|
improve this answe...
Grep regex NOT containing string
...
351
grep matches, grep -v does the inverse. If you need to "match A but not B" you usually use pipes...