大约有 30,000 项符合查询结果（耗时：0.0180秒） [XML]
String concatenation: concat() vs “+” operator
... measure, I threw in StringBuilder.append() as well. Each test was run 10 times, with 100k reps for each run. Here are the results:
StringBuilder wins hands down. The clock time result was 0 for most the runs, and the longest took 16ms.
a += b takes about 40000ms (40s) for each run.
concat only...
How can I create directory tree in C++/Linux?
...s/ss
** : ${MKPATH:=mkpath}
** ./$MKPATH $NAME &
** [...repeat a dozen times or so...]
** ./$MKPATH $NAME &
** wait
** rm -fr ./$PREFIX/
*/
int main(int argc, char **argv)
{
int i;
for (i = 1; i < argc; i++)
{
for (int j = 0; j < 20; j++)
{
...
Why isn't my Pandas 'apply' function referencing multiple columns working? [closed]
... 'c' : np.random.randn(6)})
Example 1: looping with pandas.apply():
%%timeit
def my_test2(row):
return row['a'] % row['c']
df['Value'] = df.apply(my_test2, axis=1)
The slowest run took 7.49 times longer than the fastest. This could
mean that an intermediate result is being cached. 1...
convert String to DateTime
I need to parse following String into a DateTime Object:
30/Nov/2009:16:29:30 +0100
8 Answers
...
Android Get Current timestamp?
I want to get the current timestamp like that : 1320917972
12 Answers
12
...
Create an index on a huge MySQL production table without table locking
...(and a few other things).
Test Script:
(
for n in {1..50}; do
#(time mysql -uroot -e 'select * from website_development.users where id = 41225\G'>/dev/null) 2>&1 | grep real;
(time mysql -uroot -e 'update website_development.users set bio="" where id = 41225\G'>/dev/null...
Saving timestamp in mysql table using php
I have a field in a MySQL table which has a timestamp data type. I am saving data into that table. But when I pass the timestamp ( 1299762201428 ) to the record, it automatically saves the value 0000-00-00 00:00:00 into that table.
...
How to select rows from a DataFrame based on column values?
...2
7 foo three 7 14
Note, however, that if you wish to do this many times, it is more efficient to
make an index first, and then use df.loc:
df = df.set_index(['B'])
print(df.loc['one'])
yields
A C D
B
one foo 0 0
one bar 1 2
one foo 6 12
or, to includ...
Pandas aggregate count distinct
...ms much faster, tested here on ~21M rows dataframe, then grouped to ~2M
%time _=g.agg({"id": lambda x: x.nunique()})
CPU times: user 3min 3s, sys: 2.94 s, total: 3min 6s
Wall time: 3min 20s
%time _=g.agg({"id": pd.Series.nunique})
CPU times: user 3min 2s, sys: 2.44 s, total: 3min 4s
Wall time: 3m...
Memoization in Haskell?
...his very efficiently by making a structure that we can index in sub-linear time.
But first,
{-# LANGUAGE BangPatterns #-}
import Data.Function (fix)
Let's define f, but make it use 'open recursion' rather than call itself directly.
f :: (Int -> Int) -> Int -> Int
f mf 0 = 0
f mf n = m...