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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...
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...
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...
Explain the use of a bit vector for determining if all characters are unique
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12 Answers
12
Active
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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...
What is the difference between Python's list methods append and extend?
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20 Answers
20
Active
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Counting the number of elements with the values of x in a vector
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521
You can just use table():
> a <- table(numbers)
> a
numbers
4 5 23 34 43 54 ...
Linux下安装项目管理工具Redmine - 开源 & Github - 清泛网 - 专注C/C++及内核技术
.../bin
保存退出:wq
# . .bash_profile
2、RubyGems安装
# wget http://rubyforge.org/frs/download.php/60718/rubygems-1.3.5.tgz
# tar zxvf rubygems-1.3.5.tgz
# cd rubygems-1.3.5
# ruby setup.rb
3、Rake安装
# gem install ra...