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Index all *except* one item in python
... 3rd element:
a = range(10)[::-1] # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
b = [x for i,x in enumerate(a) if i!=3] # [9, 8, 7, 5, 4, 3, 2, 1, 0]
This is very general, and can be used with all iterables, including numpy arrays. If you replace [] with (), b will be an iterator inst...
Pass a data.frame column name to a function
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edited Apr 11 '16 at 21:42
joran
152k2525 gold badges379379 silver badges431431 bronze badges
answered...
Find the max of two or more columns with pandas
...
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edited Dec 4 '16 at 19:06
alfredocambera
2,5382727 silver badges2626 bronze badges
answer...
Find XOR of all numbers in a given range
...given a large range [a,b] where 'a' and 'b' can be typically between 1 and 4,000,000,000 inclusive. You have to find out the XOR of all the numbers in the given range.
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Get the cartesian product of a series of lists?
...hon 2.6.
import itertools
somelists = [
[1, 2, 3],
['a', 'b'],
[4, 5]
]
for element in itertools.product(*somelists):
print(element)
Which is the same as,
for element in itertools.product([1, 2, 3], ['a', 'b'], [4, 5]):
print(element)
...
Why does direction of index matter in MongoDB?
...
114
MongoDB concatenates the compound key in some way and uses it as the key in a BTree.
When findi...
How to return a part of an array in Ruby?
...", "c" ]
a[1..3] #=> [ "b", "c", "d" ]
a[4..7] #=> [ "e" ]
a[6..10] #=> nil
a[-3, 3] #=> [ "c", "d", "e" ]
# special cases
a[5] #=> nil
a[6, 1] ...
Convert a row of a data frame to vector
...
answered Jan 23 '13 at 16:42
Ben BolkerBen Bolker
160k1919 gold badges286286 silver badges366366 bronze badges
...
Python creating a dictionary of lists
... 'a' is not defined
– S Andrew
Nov 14 '18 at 13:18
add a comment
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Extract elements of list at odd positions
... second at 1 etc.):
1, 3, 5
so the result (actual numbers) will be:
2, 4, 6
Explanation
The [1::2] at the end is just a notation for list slicing. Usually it is in the following form:
some_list[start:stop:step]
If we omitted start, the default (0) would be used. So the first element (at po...