大约有 1,000 项符合查询结果（耗时：0.0196秒） [XML]
Get random item from array [duplicate]
...swered Dec 23 '13 at 10:54
Naâmèn Mohamed AmineNaâmèn Mohamed Amine
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Extract subset of key-value pairs from Python dictionary object?
...works in 2.7 too):
{k: bigdict[k] for k in ('l', 'm', 'n')}
Update: As Håvard S points out, I'm assuming that you know the keys are going to be in the dictionary - see his answer if you aren't able to make that assumption. Alternatively, as timbo points out in the comments, if you want a key tha...
Does PostgreSQL support “accent insensitive” collations?
... unaccent() always substitutes a single letter:
SELECT unaccent('Œ Æ œ æ ß');
unaccent
----------
E A e a S
You will love this update to unaccent in Postgres 9.6:
Extend contrib/unaccent's standard unaccent.rules file to handle all
diacritics known to Unicode, and expand ligatures cor...
Modifying a subset of rows in a pandas dataframe
...ings
%timeit df['b'] = np.where(df.a.values == 0, np.nan, df.b.values)
685 µs ± 6.4 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
%timeit df.loc[df['a'] == 0, 'b'] = np.nan
3.11 ms ± 17.2 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
Numpy's where is about 4x faster
...
Check if something is (not) in a list in Python
... 0.613 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)
178 µs ± 5.01 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)
If you want to do more than just check whether an item is in a list, there are options:
list.index can be used to retrieve the index of an item. If t...
.gitignore is ignored by Git
...red Mar 19 '14 at 23:40
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Python string class like StringBuilder in C#?
...]: %%timeit
...: ''.join(values)
...:
100000 loops, best of 3: 7.37 µs per loop
In [3]: %%timeit
...: result = ''
...: for value in values:
...: result += value
...:
10000 loops, best of 3: 82.8 µs per loop
In [4]: import io
In [5]: %%timeit
...: writer = io.StringIO(...
Replace values in list using Python [duplicate]
....: if not (item % 2):
...: items[index] = None
...:
1.06 µs ± 33.7 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)
In [2]: %%timeit
...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
...: new_items = [x if x % 2 else None for x in items]
...:
891 ns ± 13.6 n...
How to add an extra column to a NumPy array
...b = np.hstack((a, np.zeros((a.shape[0], 1))))
100000 loops, best of 3: 7.5 µs per loop
In [4]: %timeit b = np.zeros((a.shape[0], a.shape[1]+1)); b[:,:-1] = a
100000 loops, best of 3: 2.17 µs per loop
In [5]: %timeit b = np.insert(a, 3, values=0, axis=1)
100000 loops, best of 3: 10.2 µs per loop...
Filling a DataSet or DataTable from a LINQ query result set
...wered Aug 15 '08 at 16:42
Lars MæhlumLars Mæhlum
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