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Split delimited strings in a column and insert as new rows [duplicate]
...her way of doing it..
df <- read.table(textConnection("1|a,b,c\n2|a,c\n3|b,d\n4|e,f"), header = F, sep = "|", stringsAsFactors = F)
df
## V1 V2
## 1 1 a,b,c
## 2 2 a,c
## 3 3 b,d
## 4 4 e,f
s <- strsplit(df$V2, split = ",")
data.frame(V1 = rep(df$V1, sapply(s, length)), V2 = ...
Find indices of elements equal to zero in a NumPy array
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numpy.where() is my favorite.
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.where(x == 0)[0]
array([1, 3, 5])
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How can I verify if one list is a subset of another?
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131
The performant function Python provides for this is set.issubset. It does have a few restrictio...
Iterator invalidation rules
... the iterators and references before the insertion point remain valid. [26.3.11.5/1]
With respect to the reserve function, reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence. No reallocation shall take place during insertions that happen af...
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...DBG具有非常大的灵活性和可扩展性，用来满足各种
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“ValueError: zero length field name in format” error in Python 3.0,3.1,3.2
I'm trying learn Python (3 to be more specific) and I'm getting this error:
3 Answers
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What does “SyntaxError: Missing parentheses in call to 'print'” mean in Python?
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This error message means that you are attempting to use Python 3 to follow an example or run a program that uses the Python 2 print statement:
print "Hello, World!"
The statement above does not work in Python 3. In Python 3 you need to add parentheses around the value to be printe...
Need a simple explanation of the inject method
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edited Apr 2 '09 at 16:37
answered Apr 2 '09 at 16:31
Dr...
How to add an extra column to a NumPy array
...p.random.rand(N,N)
b = np.zeros((N,N+1))
b[:,:-1] = a
And timings:
In [23]: N = 10
In [24]: a = np.random.rand(N,N)
In [25]: %timeit b = np.hstack((a,np.zeros((a.shape[0],1))))
10000 loops, best of 3: 19.6 us per loop
In [27]: %timeit b = np.zeros((a.shape[0],a.shape[1]+1)); b[:,:-1] = a
10000...
How to join two sets in one line without using “|”
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320
You can use union method for sets: set.union(other_set)
Note that it returns a new set i.e it...