54
votes
3
answers
2.6K
views
What is the difference between flatten and ravel functions in numpy?
import numpy as np y = np.array(((1,2,3),(4,5,6),(7,8,9))) OUTPUT: print(y.flatten()) [1 2 3 4 5 6
60
votes
9
answers
1.3K
views
Creating a Pandas DataFrame from a Numpy array: How do I specify the index column and column headers?
I have a Numpy array consisting of a list of lists, representing a two-dimensional array with row labels and c
53
votes
13
answers
2.3K
views
Converting between datetime, Timestamp and datetime64
How do I convert a numpy.datetime64 object to a datetime.datetime (or Timestamp)? In the following code, I cr
65
votes
6
answers
1.5K
views
What is the difference between Numpy's array() and asarray() functions?
What is the difference between Numpy's array() and asarray() functions? When should you use one rather th
52
votes
5
answers
608
views
Converting NumPy array into Python List structure?
How do I convert a NumPy array to a Python List (for example [[1,2,3],[4,5,6]] ), and do it reasonably fast?
55
votes
17
answers
3.1K
views
How to add an extra column to a NumPy array
Let’s say I have a NumPy array, a: a = np.array([ [1, 2, 3], [2, 3, 4] ]) And I would like
55
votes
15
answers
782
views
How do I create an empty array/matrix in NumPy?
I can't figure out how to use an array or matrix in the way that I would normally use a list. I want to c
54
votes
7
answers
1.3K
views
Difference between numpy.array shape (R, 1) and (R,)
In numpy, some of the operations return in shape (R, 1) but some return (R,). This will make matrix multiplica
53
votes
14
answers
1.8K
views
How to pretty-print a numpy.array without scientific notation and with given precision?
I'm curious, whether there is any way to print formatted numpy.arrays, e.g., in a way similar to this: x
61
votes
11
answers
1.4K
views
What does numpy.random.seed(0) do?
What does np.random.seed do in the below code from a Scikit-Learn tutorial? I'm not very familiar with Nu
62
votes
5
answers
560
views
What are the differences between numpy arrays and matrices? Which one should I use?
What are the advantages and disadvantages of each? From what I've seen, either one can work as a replace
53
votes
10
answers
2.5K
views
Pandas conditional creation of a series/dataframe column
I have a dataframe along the lines of the below: Type Set 1 A Z 2 B Z
64
votes
18
answers
809
views
Find nearest value in numpy array
Is there a numpy-thonic way, e.g. function, to find the nearest value in an array? Example: np.find_nearest
69
votes
7
answers
437
views
What is the purpose of meshgrid in Python / NumPy?
Can someone explain to me what is the purpose of meshgrid function in Numpy? I know it creates some kind of gr
66
votes
3
answers
410
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
65
votes
8
answers
412
views
Numpy array dimensions
I'm currently trying to learn Numpy and Python. Given the following array: import numpy as np a = np.arr
48
votes
15
answers
432
views
Sorting arrays in NumPy by column
How can I sort an array in NumPy by the nth column? For example, a = array([[9, 2, 3], [4, 5, 6],
60
votes
10
answers
1.8K
views
Pandas read_csv low_memory and dtype options
When calling df = pd.read_csv('somefile.csv') I get: /Users/josh/anaconda/envs/py27/lib/pytho
59
votes
7
answers
2.9K
views
pandas create new column based on values from other columns / apply a function of multiple columns, row-wise
I want to apply my custom function (it uses an if-else ladder) to these six columns (ERI_Hispanic, ERI_AmerInd
55
votes
17
answers
1.5K
views
How to find all occurrences of an element in a list
index() will give the first occurrence of an item in a list. Is there a neat trick which returns all indices i
