大约有 47,000 项符合查询结果（耗时：0.0668秒） [XML]
python list by value not by reference [duplicate]
... import timeit
In [2]: timeit.timeit('b.extend(a)', setup='b=[];a=range(0,10)', number=100000000)
Out[2]: 9.623248100280762
In [3]: timeit.timeit('b = a[:]', setup='b=[];a=range(0,10)', number=100000000)
Out[3]: 10.84756088256836
In [4]: timeit.timeit('b = list(a)', setup='b=[];a=range(0,10)', nu...
How to get the last N records in mongodb?
...
answered Dec 13 '10 at 1:23
Justin JenkinsJustin Jenkins
23.5k55 gold badges6161 silver badges12831283 bronze badges
...
Oracle 11.2.0.4 RAC FOR redhat 6.4 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
...lhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.110.100 dmjyrac1
172.16.110.101 dmjyrac1-vip
172.16.110.110 dmjyrac2
172.16.110.111 dmjyrac2-vip
172.16.110.102 dmjyrac-cluster dmjyrac-cluster-scan
10.10.120.100 dmjyrac1-priv
10.10.120.110 dm...
How can I increment a char?
...ord and chr functions:
>>> ord('c')
99
>>> ord('c') + 1
100
>>> chr(ord('c') + 1)
'd'
>>>
Python 3.x makes this more organized and interesting, due to its clear distinction between bytes and unicode. By default, a "string" is unicode, so the above works (ord r...
Scala: List[Future] to Future[List] disregarding failed futures
...equence(...) but there's a twist... The list I'm given usually has around 10-20 futures in it, and it's not uncommon for one of those futures to fail (they are making external web service requests). Instead of having to retry all of them in the event that one of them fails, I'd like to be able to g...
Multiline bash commands in makefile
...
answered Apr 12 '12 at 10:13
Eldar AbusalimovEldar Abusalimov
20k44 gold badges5656 silver badges6565 bronze badges
...
How exactly does the “Specific Version” property of an assembly reference work in Visual Studio?
... the "Specific Version" property of assembly references in Visual Studio 2010. After a few experiments with unexpected results I set out to learn as much as possible about how the property works. Even SO, it appears to me, does not have all the answers, so here is my attempt at self-answering the qu...
SELECT INTO using Oracle
... |
edited Dec 9 '19 at 10:48
answered Feb 12 '10 at 7:22
...
Remove duplicated rows using dplyr
...ow:
library(dplyr)
set.seed(123)
df <- data.frame(
x = sample(0:1, 10, replace = T),
y = sample(0:1, 10, replace = T),
z = 1:10
)
One approach would be to group, and then only keep the first row:
df %>% group_by(x, y) %>% filter(row_number(z) == 1)
## Source: local data frame [...
Comparing two dictionaries and checking how many (key, value) pairs are equal
...
answered Dec 24 '10 at 19:17
mouadmouad
55.9k1515 gold badges107107 silver badges102102 bronze badges
...