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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...
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 = ...
What does “SyntaxError: Missing parentheses in call to 'print'” mean in Python?
...
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...
Find indices of elements equal to zero in a NumPy array
...
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 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...
Output data from all columns in a dataframe in pandas [duplicate]
...
Erel Segal-Halevi
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answered Nov 5 '12 at 18:13
YarivYariv
...
Need a simple explanation of the inject method
... |
edited Apr 2 '09 at 16:37
answered Apr 2 '09 at 16:31
Dr...
How to join two sets in one line without using “|”
...
320
You can use union method for sets: set.union(other_set)
Note that it returns a new set i.e it...
php中json_decode()和json_encode()的使用方法 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...Example #1 json_decode() 的例子
<?php
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));
var_dump(json_decode($json, true));
?>
上例将输出：
object(stdClass)#1 (5) {
["a"] => int(1)
["b"] => int(2)
["c"] => int(3)
["d"] => int(4)
["e"] => i...
用矩阵管理成绩表 - App Inventor 2 矩阵块入门案例 · App Inventor 2 中文网
...：把成绩表装进矩阵
第 2 关：查任意一格的成绩
第 3 关：改成绩（原地修改）
第 4 关：算某一行（某名学生）的平均分
第 5 关：整表转置，横过来看
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