大约有 44,100 项符合查询结果（耗时：0.0491秒） [XML]
Combine two or more columns in a dataframe into a new column with a new name
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132
Use paste.
df$x <- paste(df$n,df$s)
df
# n s b x
# 1 2 aa TRUE 2 aa
# 2 3 bb F...
How to limit depth for recursive file list?
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edited Dec 22 '10 at 13:39
answered Dec 22 '10 at 13:31
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Why can't I use a list as a dict key in python?
...uality. Many would - understandably - expect that you can use any list [1, 2] to get the same key, where you'd have to keep around exactly the same list object. But lookup by value breaks as soon as a list used as key is modified, and for lookup by identity requires you to keep around exactly the sa...
Rank items in an array using Python/NumPy, without sorting array twice
...se slicing on the left-hand side in the last step:
array = numpy.array([4,2,7,1])
temp = array.argsort()
ranks = numpy.empty_like(temp)
ranks[temp] = numpy.arange(len(array))
This avoids sorting twice by inverting the permutation in the last step.
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What does |= (ior) do in Python?
...e examples below.
Sets
For example, the union of two assigned sets s1 and s2 share the following equivalent expressions:
>>> s1 = s1 | s12 # 1
>>> s1 |= s2 # 2
>>> s1.__ior__(s2) ...
How can I obtain the element-wise logical NOT of a pandas Series?
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274
To invert a boolean Series, use ~s:
In [7]: s = pd.Series([True, True, False, True])
In [8]:...
How do I use the conditional operator (? :) in Ruby?
...t for precedence issues. Both are expressions.
Examples:
puts (if 1 then 2 else 3 end) # => 2
puts 1 ? 2 : 3 # => 2
x = if 1 then 2 else 3 end
puts x # => 2
Note that in the first case parenthesis are required (otherwise Ruby is confused because i...
Linq style “For Each” [duplicate]
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288
Using the ToList() extension method is your best option:
someValues.ToList().ForEach(x => ...
Using multiple let-as within a if-statement in Swift
...itudeDouble is non-optional in here and importantThing is true
}
Swift 1.2:
Apple may have read your question, because your hoped-for code compiles properly in Swift 1.2 (in beta today):
if let latitudeDouble = latitude as? Double, longitudeDouble = longitude as? Double {
// do stuff here
}
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In Python, how do I iterate over a dictionary in sorted key order?
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Haven't tested this very extensively, but works in Python 2.5.2.
>>> d = {"x":2, "h":15, "a":2222}
>>> it = iter(sorted(d.iteritems()))
>>> it.next()
('a', 2222)
>>> it.next()
('h', 15)
>>> it.next()
('x', 2)
>>>
If you are us...