# All Questions

**130**

votes

**20**answers

53547 views

### Find unique rows in numpy.array

I need to find unique rows in a numpy.array.
For example:
>>> a # I have
array([[1, 1, 1, 0, 0, 0],
[0, 1, 1, 1, 0, 0],
[0, 1, 1, 1, 0, 0],
[1, 1, 1, 0, 0, 0],
[...

**88**

votes

**7**answers

60089 views

### Using numpy to build an array of all combinations of two arrays

I'm trying to run over the parameters space of a 6 parameter function to study it's numerical behavior before trying to do anything complex with it so I'm searching for a efficient way to do this.
My...

**64**

votes

**5**answers

35162 views

### Use numpy array in shared memory for multiprocessing

I would like to use a numpy array in shared memory for use with the multiprocessing module. The difficulty is using it like a numpy array, and not just as a ctypes array.
from multiprocessing import...

**47**

votes

**7**answers

24327 views

### Numpy: cartesian product of x and y array points into single array of 2D points

I have two numpy arrays that define the x and y axes of a grid. For example:
x = numpy.array([1,2,3])
y = numpy.array([4,5])
I'd like to generate the Cartesian product of these arrays to generate:...

**63**

votes

**11**answers

32965 views

### Split (explode) pandas dataframe string entry to separate rows

I have a pandas dataframe in which one column of text strings contains comma-separated values. I want to split each CSV field and create a new row per entry (assume that CSV are clean and need only be...

**24**

votes

**3**answers

4988 views

### What is the difference between size and count in pandas?

That is the difference between groupby("x").count and groupby("x").size in pandas ?
Does size just exclude nil ?

**6**

votes

**5**answers

1067 views

### Find the row indexes of several values in a numpy array

I have an array X:
X = np.array([[4, 2],
[9, 3],
[8, 5],
[3, 3],
[5, 6]])
And I wish to find the index of the row of several values in t...

**8**

votes

**1**answers

1271 views

### Taking subarrays from numpy array with given stride/stepsize

Lets say I have a Python Numpy array array a.
numpy.array([1,2,3,4,5,6,7,8,9,10,11].)
I want to create a matrix of sub sequences from this array of length 5 with stride 3. The results matrix hence ...

**322**

votes

**6**answers

102209 views

### Why NumPy instead of Python lists?

Is it worth my learning NumPy?
I have approximately 100 financial markets series, and I am going to create a cube array of 100x100x100 = 1 million cells. I will be regressing (3-variable) each x with...

**305**

votes

**3**answers

162223 views

### Simple Digit Recognition OCR in OpenCV-Python

I am trying to implement a "Digit Recognition OCR" in OpenCV-Python (cv2). It is just for learning purposes. I would like to learn both KNearest and SVM features in OpenCV.
I have 100 samples (i.e. ...