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How to count the number of true elements in a NumPy bool array
I have a NumPy array 'boolarr' of boolean type. I want to count the number of elements whose values are True . Is there a NumPy or Python routine dedicated for this task? Or, do I need to iterate over the elements in my script?
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How can I reverse a list in Python?
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You can make use of the reversed function for this as:
>>> array=[0,10,20,40]
>>> for i in reversed(array):
... print(i)
Note that reversed(...) does not return a list. You can get a reversed list using list(reversed(array)).
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What is the equivalent of MATLAB's repmat in NumPy
... dimensions and gives a similar result to matlab. (Numpy gives a 3d output array as you would expect - matlab for some reason gives 2d output - but the content is the same).
Matlab:
>> repmat([1;1],[1,1,1])
ans =
1
1
Python:
In [46]: a = np.array([[1],[1]])
In [47]: np.tile(a, ...
How to get the index of a maximum element in a numpy array along one axis
I have a 2 dimensional NumPy array. I know how to get the maximum values over axes:
4 Answers
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How to extract numbers from a string and get an array of ints?
...ecified number of numbers) and I'd like to extract all the numbers into an array of integers. I was wondering whether there was a quick solution with regular expressions?
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How to convert int[] to Integer[] in Java?
...ed to Integer[] easily:
int[] data = {1,2,3,4,5,6,7,8,9,10};
// To boxed array
Integer[] what = Arrays.stream( data ).boxed().toArray( Integer[]::new );
Integer[] ever = IntStream.of( data ).boxed().toArray( Integer[]::new );
// To boxed list
List<Integer> you = Arrays.stream( data ).boxed...
Java: int array initializes with nonzero elements
According to the JLS, an int array should be filled by zeros just after initialization. However, I am faced with a situation where it is not. Such a behavior occurs first in JDK 7u4 and also occurs in all later updates (I use 64-bit implementation). The following code throws exception:
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'and' (boolean) vs '&' (bitwise) - Why difference in behavior with lists vs numpy arrays?
...difference in behavior of boolean and bitwise operations on lists vs NumPy arrays?
8 Answers
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Logical operators for boolean indexing in Pandas
... Python to convert (a['x']==1) and (a['y']==10) to boolean values.
NumPy arrays (of length greater than 1) and Pandas objects such as Series do not have a boolean value -- in other words, they raise
ValueError: The truth value of an array is ambiguous. Use a.empty, a.any() or a.all().
when use...
Position of least significant bit that is set
... It seems to me that both value 0x01 and 0x00 result in value 0 from the array. Apparently this trick will indicate that the lowest bit is set if 0 is passed in!
– abelenky
Sep 16 '16 at 3:16
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