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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...
Detect 7 inch and 10 inch tablet programmatically
...gth of the hypotenuse (In this case, the size of the screen diagonal).
//a² + b² = c²
//The size of the diagonal in inches is equal to the square root of the height in inches squared plus the width in inches squared.
double diagonalInches = Math.sqrt(
(widthInches * widthInches)
+ (hei...
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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2,31033 gold badges1414 silver badges2424 bronze badges
...
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...
AI跳舞 · App Inventor 2 中文网
...理计算两个点在 Canvas 上的欧氏距离：
距离 = √((x2 - x1)² + (y2 - y1)²)
只有两个点都定义时才计算距离。这个过程之后会用于判断手臂是否伸直，以及 T 形姿势中手腕到肩膀的距离。
8. 创建绘制关键点和骨骼的过程
创建 dra...
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...
How do I select elements of an array given condition?
...that an intermediate result is being cached.
100000 loops, best of 3: 1.15 µs per loop
>>> %timeit np.logical_and(a < b, b < c)
The slowest run took 32.59 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 1.17 µs p...