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How to group dataframe rows into list in pandas groupby?
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12 Answers
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What is the syntax to insert one list into another list in python?
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Do you mean append?
>>> x = [1,2,3]
>>> y = [4,5,6]
>>> x.append(y)
>>> x
[1, 2, 3, [4, 5, 6]]
Or merge?
>>> x = [1,2,3]
>>> y = [4,5,6]
>>> x + y
[1, 2, 3, 4, 5, 6]
>>> x.extend(y)
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SQL query return data from multiple tables
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472
Part 1 - Joins and Unions
This answer covers:
Part 1
Joining two or more tables using an in...
How to iterate for loop in reverse order in swift?
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233
Xcode 6 beta 4 added two functions to iterate on ranges with a step other than one:
stride(fro...
Explain the use of a bit vector for determining if all characters are unique
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12 Answers
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Normalize data in pandas
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226
In [92]: df
Out[92]:
a b c d
A -0.488816 0.863769 4.32...
Understanding dict.copy() - shallow or deep?
...pied by value, but just creating a new reference.
>>> a = {1: [1,2,3]}
>>> b = a.copy()
>>> a, b
({1: [1, 2, 3]}, {1: [1, 2, 3]})
>>> a[1].append(4)
>>> a, b
({1: [1, 2, 3, 4]}, {1: [1, 2, 3, 4]})
In contrast, a deep copy will copy all contents by valu...
What is the difference between Python's list methods append and extend?
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20 Answers
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Element-wise addition of 2 lists?
...t;>> from operator import add
>>> list( map(add, list1, list2) )
[5, 7, 9]
or zip with a list comprehension:
>>> [sum(x) for x in zip(list1, list2)]
[5, 7, 9]
Timing comparisons:
>>> list2 = [4, 5, 6]*10**5
>>> list1 = [1, 2, 3]*10**5
>>> %tim...