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Waiting until two async blocks are executed before starting another block
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305
Use dispatch groups: see here for an example, "Waiting on Groups of Queued Tasks" in the "Disp...
Python, compute list difference
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373
If the order does not matter, you can simply calculate the set difference:
>>> set([...
How do I exchange keys with values in a dictionary?
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Python 2:
res = dict((v,k) for k,v in a.iteritems())
Python 3 (thanks to @erik):
res = dict((v,k) for k,v in a.items())
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How to group dataframe rows into list in pandas groupby?
..., 'b':[1,2,5,5,4,6]})
df
Out[1]:
a b
0 A 1
1 A 2
2 B 5
3 B 5
4 B 4
5 C 6
In [2]: df.groupby('a')['b'].apply(list)
Out[2]:
a
A [1, 2]
B [5, 5, 4]
C [6]
Name: b, dtype: object
In [3]: df1 = df.groupby('a')['b'].apply(list).reset_index(name='new')
...
How to calculate moving average using NumPy?
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173
If you just want a straightforward non-weighted moving average, you can easily implement it with...
map function for objects (instead of arrays)
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38 Answers
38
Active
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Pandas: create two new columns in a dataframe with values calculated from a pre-existing column
... from pandas import *
In [2]: def calculate(x):
...: return x*2, x*3
...:
In [3]: df = DataFrame({'a': [1,2,3], 'b': [2,3,4]})
In [4]: df
Out[4]:
a b
0 1 2
1 2 3
2 3 4
In [5]: df["A1"], df["A2"] = zip(*df["a"].map(calculate))
In [6]: df
Out[6]:
a b A1 A2
0 1 2 2...
Python - Create list with numbers between 2 values?
...t returns a list so all you need is:
>>> range(11, 17)
[11, 12, 13, 14, 15, 16]
In Python 3.x range is a iterator. So, you need to convert it to a list:
>>> list(range(11, 17))
[11, 12, 13, 14, 15, 16]
Note: The second number is exclusive. So, here it needs to be 16+1 = 17
E...
Why are Python lambdas useful? [closed]
...where you can pass functions to other functions to do stuff. Example:
mult3 = filter(lambda x: x % 3 == 0, [1, 2, 3, 4, 5, 6, 7, 8, 9])
sets mult3 to [3, 6, 9], those elements of the original list that are multiples of 3. This is shorter (and, one could argue, clearer) than
def filterfunc(x):
...