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Python NumPy Programs

NumPy is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, along with a large collection of high-level mathematical functions to operate on these arrays.

This section contains the solved programs on Python NumPy, practice these programs to learn the concept of Python NumPy. These programs contain the solved code, explanation, and output used in the Python NumPy programs.

List of Python NumPy Programs

1. Convert pandas dataframe to NumPy array
2. What does -1 mean in numpy reshape?
3. How can the Euclidean distance be calculated with NumPy?
4. Convert a NumPy array into a CSV file
5. How to get the n-largest values of an array using NumPy?
6. How do I access the ith column of a NumPy multidimensional array?
7. How do I print the full NumPy array, without truncation?
8. Most efficient way to map function over numpy array
9. How to count the occurrence of a certain item in a ndarray?
10. Is there a NumPy function to return the first index of something in an array?
11. Pretty-print a NumPy array without scientific notation and with given precision
12. What does numpy.random.seed() do?
13. Sorting arrays in NumPy by column
14. How do I read CSV data into a record array in NumPy?
15. Convert 2D float array to 2D int array in NumPy
16. Most efficient way to reverse a NumPy array
17. NumPy array initialization (fill with identical values)
18. How to remove NaN values from a given NumPy array?
19. How do I use np.newaxis?
20. NumPy matrix vector multiplication
21. Convert a tensor to numpy array in Tensorflow?
22. How to remove specific elements in a numpy array?
23. Better way to shuffle two numpy arrays in unison
24. Convert array of indices to one-hot encoded array in NumPy?
25. Create numpy matrix filled with NaNs
26. How to create a numpy array of all True or all False?
27. Transposing a 1D NumPy Array
28. NumPy Array: Moving Average or Running Mean
29. How to calculate percentiles in NumPy array?
30. Is it possible to use numpy.argsort() in descending order?
31. How to Convert List of Lists to NumPy Array?
32. Find unique rows in a NumPy array
33. How to check whether a numpy array is empty or not?
34. Replace all elements of Python NumPy Array that are greater than some value
35. How to add a new row to an empty NumPy array?
36. Extracting specific columns in NumPy array
37. NumPy: Get random set of rows from 2D array
38. 'Cloning' row or column vectors
39. How to flatten only some dimensions of a NumPy array?
40. numpy.mean() vs numpy.average() in NumPy
41. Concatenate a NumPy array to another NumPy array
42. How to split data into 3 sets (train, validation and test)?
43. How to count the number of true elements in a NumPy bool array?
44. Add row to a NumPy array
45. How do you get the magnitude of a vector in NumPy?
46. What is the inverse function of zip?
47. NumPy: Divide each row by a vector element
48. Find the most frequent value in a NumPy array
49. How to convert an array of strings to an array of floats in NumPy?
50. How to index every element in a list except one?
51. Add single element to array in numpy
52. Detect if a NumPy array contains at least one non numeric value
53. Convert numpy array to tuple
54. NumPy: How to iterate over columns of array?
55. NumPy: How to return 0 with divide by zero?
56. Finding local maxima/minima with NumPy in a 1D NumPy array
57. How to install SciPy and NumPy using pip?
58. How to get the index of a maximum element in a NumPy array along one axis?
59. How to write a multidimensional array to a text file?
60. Fast check for NaN in NumPy
61. Generate random array of floats between a range
62. How do you use the ellipsis slicing syntax?
63. What does 'three dots' mean when indexing what looks like a number?
64. How to find the length (or dimensions, size) of a NumPy matrix?
65. How to select elements of an array given condition?
66. Test if NumPy array contains only zeros
67. NumPy selecting specific column index per row by using a list of indexes
68. How can I remove Nan from list NumPy array?
69. How to determine whether a column/variable is numeric or not in Pandas/NumPy?
70. NumPy Machine Epsilon
71. Multiple Linear Regression
72. NumPy: function for simultaneous max() and min()
73. In-place type conversion of a NumPy array
74. Best way to assert for numpy.array() equality?
75. Rank items in an array using NumPy, without sorting array twice
76. Subsampling every nth entry in a NumPy array
77. How does multiplication differ for NumPy Matrix vs Array classes?
78. What is the difference between NaN and None?
79. How to delete a batch of rows of a NumPy array simultaneously?
80. Python - How to remove specific elements from a NumPy array?
81. Stack summing vectors to numpy 3d array
82. How to sum by year using NumPy?
83. How to turn a 3d numpy array into a pandas dataframe of numpy 1d arrays?
84. How to use numpy.arange() with pandas Series?
85. Select records of specific data type from numpy recarray
86. Calculating a rolling (weighted) average using numpy
87. Converting a 3D NumPy array to coordinates and values
88. How to add a 4x4 matrix values into a 6x6 matrix using numpy?
89. How to print a unit matrix?
90. NumPy: How to make a moving(growing) sum of table contents without a for loop?
91. Solving Systems of Linear Equations with Python's NumPy
92. How to calculate cumulative normal distribution?
93. How can I use numpy.correlate() to do autocorrelation?
94. How to save a list as NumPy array?
95. numpy.logical_or() for more than two arguments
96. How to pad NumPy array with zeros?
97. NumPy index slice without losing dimension information
98. What exactly does numpy.exp() do?
99. What is the difference between i+1 and i += 1 in a for loop with NumPy?
100. Non-repetitive random number in NumPy
101. NumPy array assignment with copy
102. Replacing NumPy elements if condition is met
103. Efficiently checking if arbitrary object is NaN in NumPy?
104. How to remove all rows in a numpy ndarray that contain non numeric values?
105. Convert 2d numpy array into list of lists
106. Shift elements in a NumPy array
107. How does NumPy's transpose() method permute the axes of an array?
108. How to get the indices list of all NaN value in NumPy array?
109. Convert nan value to zero in NumPy array
110. NumPy: Find first index of value fast
111. Find the index of the k smallest values of a NumPy array
112. Interweaving two numpy arrays
113. Replace negative values in a numpy array
114. Translate every element in numpy array according to key
115. Add NumPy array as column to Pandas dataframe
116. List to array conversion to use ravel() function
117. What is the difference between np.mean() and tf.reduce_mean()?
118. Calculate mean across dimension in a 2D array
119. How to create a numpy array of arbitrary length strings?
120. How does python numpy.where() work?
121. How does numpy.std() method work?
122. Is there a multi-dimensional version of arange/linspace in numpy?
123. How to copy data from a NumPy array to another?
124. Why does corrcoef return a matrix?
125. Comparing numpy arrays containing NaN
126. shuffle vs permute numpy
127. Partition array into N chunks with NumPy
128. Maximum allowed value for a numpy data type
129. 'isnotnan' functionality in numpy, can this be more pythonic?
130. Get the position of the largest value in a multi-dimensional NumPy array
131. How do you find the IQR in NumPy?
132. NumPy's mean() and nanmean() Methods
133. How to make numpy.argmax() return all occurrences of the maximum?
134. Averaging over every n elements of a NumPy array
135. How to find the groups of consecutive elements in a NumPy array?
136. Count all values in a matrix less than a value
137. Concatenate (or clone) a NumPy array N times
138. Differentiating between row and column vectors
139. Why are 0d arrays in Numpy not considered scalar?
140. Concatenate two NumPy arrays vertically
141. How can I tell if NumPy creates a view or a copy?
142. How to solve a pair of nonlinear equations?
143. Load CSV into 2D matrix with NumPy for plotting
144. Find out if matrix is positive definite with numpy
145. Prepend element to numpy array
146. Determining duplicate values in an array
147. How to inverse a matrix using NumPy?
148. How to perform element-wise Boolean operations on NumPy arrays?
149. How to calculate the sum of all columns of a 2D numpy array (efficiently)?
150. How to turn a boolean array into index array in numpy?
151. How to upgrade NumPy?
152. How to use numpy.savetxt() to write strings and float number to an ASCII file?
153. How to round a numpy array?
154. How does condensed distance matrix (cdist) work?
155. NumPy: Creating a complex array from 2 real ones?
156. What is an intuitive explanation of numpy.unravel_index()?
157. Calculate average values of two given NumPy arrays
158. Built-in range() or numpy.arange(): which is more efficient?
159. Why is numpy's einsum faster than numpy's built in functions?
160. NumPy: Slice of arbitrary dimensions
161. Importing PNG files into NumPy
162. Rearrange columns of NumPy 2D array
163. Calculating Covariance using numpy.cov() method
164. Set numpy array elements to zero if they are above a specific threshold
165. Ignore divide by 0 warning in NumPy
166. How can I 'zip sort' parallel numpy arrays?
167. NumPy: Shuffle multidimensional array by row only, keep column order unchanged
168. Easy way to test if each element in a numpy array lies between two values?
169. Elegant way to perform tuple arithmetic
170. Factorial in numpy and scipy
171. How to zip two 1d numpy array to 2d numpy array?
172. Are numpy arrays passed by reference?
173. Test array values for NaT (not a time) in NumPy
174. Array slice with comma
175. Check whether a Numpy array contains a specified row
176. Initialise numpy array of unknown length
177. Interpolate NaN values in a numpy array
178. What does numpy.gradient() do?
179. Use numpy's any() and all() methods
180. Sort array's rows by another array
181. How to add items into a numpy array?
182. NumPy minimum in (row, column) format
183. How to swap columns in a numpy array?
184. Check if numpy array is multidimensional or not
185. Function to determine if two numbers are nearly equal when rounded to n significant decimal digits
186. Check how many elements are equal in two numpy arrays?
187. How to transform negative elements to zero without a loop?
188. NumPy: Extract Submatrix
189. NumPy: Subtract every row of matrix by vector
190. NumPy: Divide row by row sum
191. How to apply a function / map values of each element in a 2d numpy array/matrix?
192. Slice 2d array into smaller 2d arrays
193. How to Remove Duplicate Elements from NumPy Array?
194. Recover dict from 0-d numpy array
195. Difference between numpy dot() and inner() Methods
196. Iterating over NumPy matrix rows to apply a function each?
197. numpy.unique() method with order preserved
198. NumPy vstack vs. column_stack
199. Conditionally fill column values based on another columns value in Pandas
200. What is the equivalent of zip() in NumPy?
201. NumPy: For every element in one array, find the index in another array
202. Concatenating empty array in NumPy
203. Fast replacement of values in a NumPy array
204. Find the min/max excluding zeros in a numpy array (or a tuple)
205. What are some possible calculations with numpy or scipy that can return a NaN?
206. How to store different datatypes in one NumPy array?
207. How to rearrange array based on index array?
208. NumPy: Remove a dimension from np array
209. What are the advantages of using numpy.identity over numpy.eye?
210. Extracting first n columns of a NumPy matrix
211. Size of data type using NumPy
212. Get the column names of a NumPy ndarray
213. Normalize NumPy Array Columns
214. Zero pad numpy array
215. String representation of a numpy array with commas separating its elements
216. How to get the range of valid Numpy data types?
217. numpy.sin() function in degrees
218. numpy.random.rand() vs numpy.random.random() Methods
219. How to understand NumPy strides for layman?
220. Swapping the dimensions of a NumPy array
221. Good ways to 'expand' a NumPy ndarray
222. Simplest way to extend a NumPy array in 2 dimensions
223. Find matching rows in 2 dimensional NumPy array
224. Why in NumPy 'nan == nan' is False while nan in [nan] is True?
225. NumPy Meshgrid Function
226. What does the 'keepdims' parameter do with numpy.sum() function?
227. Replace -inf with zero value in NumPy array
228. Fast way to find the n-largest values of an array using NumPy
229. Using NumPy Vectorize on Functions that Return Vectors
230. What does numpy ndarray shape do?
231. Sliding window of MxN shape numpy.ndarray()
232. What is the difference between np.linspace() and np.arange() methods?
233. How to convert list of numpy arrays into single numpy array?
234. Is there a head and tail method for NumPy array?
235. How to multiply each element in a list by a number?
236. How to get all the values from a NumPy array excluding a certain index?
237. How to perform max/mean pooling on a 2d array using numpy?
238. NumPy: Efficiently avoid 0s when taking log (matrix)
239. Replace NaN values with average of columns in NumPy array
240. What is the purpose of numpy.where() returning a tuple?
241. How to slice a numpy array along a dynamically specified axis?
242. How to save arrays as columns with numpy.savetxt()?
243. Efficiently count zero elements in numpy array
244. R summary() equivalent in numpy
245. How does numpy.fft.fft() work?
246. Weighted choice short and simple
247. Select elements of numpy array via boolean mask array
248. Multiply several matrices in numpy
249. Is there a numpy/scipy dot product, calculating only the diagonal entries of the result?
250. How to use numpy.where() with logical operators?
251. How to square or raise to a power (elementwise) a 2D numpy array?
252. How to get the values from a NumPy array using multiple indices?
253. How to print numpy array with 3 decimal places?
254. How to extract frequency associated with fft values?
255. How to generate a dense matrix from a sparse matrix in NumPy?
256. Difference between two NumPy arrays
257. How to convert two lists into a matrix?
258. How to convert map object to NumPy array?
259. How to copy NumPy array into part of another array?
260. How to convert byte array back to NumPy array?
261. NumPy: Multiply array with scalar
262. What is the numpy.dstack() function in NumPy?
263. How to convert a dictionary to NumPy structured array?
264. How to loop through 2D NumPy array using x and y coordinates without getting out of bounds error?
265. Is there a NumPy function that allows you to specify start, step, and number?
266. NumPy: Boolean array with 1 bit entries
267. How to change a single value in a NumPy array?
268. Is there a way to check if NumPy arrays share the same data?
269. Weird behaviour initializing a NumPy array of string data
270. How does the axis parameter from NumPy work?
271. How to set max output width in NumPy?
272. Scipy Sparse Arrays
273. Module 'numpy' has no attribute 'arrange' (Fixed)
274. Why the output of numpy.where(condition) is not an array, but a tuple of arrays?
275. Is there any function to reduce fractions?
276. numpy.argmax(): Random tie breaking
277. How to print a NumPy array without brackets?
278. What's the difference between nonzero(a), where(a) and argwhere(a)?
279. What does selection by [:,None] do in NumPy?
280. numpy.squeeze() Method | Why do we need numpy.squeeze()?
281. How to convert NumPy array type and values from Float64 to Float32?
282. How to save dictionaries through numpy.save()?
283. How to multiply two vector and get a matrix?
284. How to find index where elements change value NumPy?
285. How to plot vectors using matplotlib?
286. How to check if all values in the columns of a NumPy matrix are the same?
287. How to find first non-zero value in every column of a NumPy array?
288. How to get intersecting rows across two 2D NumPy arrays?
289. Set very low values to zero in NumPy
290. NumPy: Appending to file using savetxt()
291. How to convert a numpy.ndarray to string(or bytes) and convert it back to numpy.ndarray?
292. scipy.stats seed
293. Available datatypes for 'dtype' with NumPy's loadtxt() an genfromtxt
294. How to check if a matrix is symmetric in NumPy?
295. Convert list or NumPy array of single element to float
296. How to make a 2d NumPy array a 3d array?
297. How to get the determinant of a matrix using NumPy?
298. How to get the element-wise mean of a NumPy ndarray?
299. How to count values in a certain range in a NumPy array?
300. Elementwise multiplication of a scipy.sparse matrix by a broadcasted dense 1d array
301. How to apply a lookup table to a large array in NumPy?
302. How to get the indices of the sorted array using NumPy?
303. How to calculate the minimum Euclidean distance between points in two different NumPy arrays?
304. numpy.repeat() Method with Example
305. numpy.eye() Method with Example
306. numpy.polyval() Method with Example
307. numpy.digitize() Method with Example
308. numpy.polyfit() Method with Example
309. numpy.random.binomial() Method with Example
310. How to crop center portion of a NumPy image?
311. Difference between randn() and normal() functions
312. What is double colon (::) in NumPy like in arr[0::3]?
313. What does [:, :] mean on NumPy arrays?
314. Difference between flip() and fliplr() functions in NumPy
315. Distance between point and a line from two points in NumPy
316. numpy.max() or max(), which one is faster?
317. Dictionary keys and values to separate NumPy arrays
318. Index a 2D NumPy array with 2 lists of indices
319. How to remove zeroes from the beginning of a NumPy array?
320. Difference between numpy.insert() and numpy.append() functions
321. How to Convert a Set to a NumPy Array?
322. How to get indices of elements that are greater than a threshold in 2D NumPy array?
323. How to index a NumPy array with another NumPy array?
324. Difference between numpy.frompyfunc() and numpy.vectorize() functions
325. How numpy.histogram() function works?
326. numpy.vander() Method with Example
327. numpy.copyto() Method with Example
328. NumPy Array: Row major and column major
329. How to zip two 2D NumPy arrays?
330. What's the fastest way to generate delimited string from 1d NumPy array?
331. How to write a raw binary file with NumPy array data?
332. Index multiple, non-adjacent ranges in NumPy?
333. How to concatenate 2D arrays with 1D array in NumPy?
334. Does setting NumPy arrays to None free memory?
335. How to interpret the values returned by numpy.correlate()?
336. How to replace sub part of matrix by another small matrix in NumPy?
337. NumPy: Adding two vectors with different sizes
338. How to find range of a NumPy array elements?
339. How to perform outer addition with NumPy?
340. How to fix array with rows of different lengths by filling the empty elements with zeros?
341. How to scale a NumPy array?
342. How to convert singleton array to a scalar value?
343. NumPy: What's the best way to remove the last element from 1 dimensional array?
344. How to fix 'ValueError: The requested array has an inhomogeneous shape after 1 dimensions'?
345. How to get a contiguous array in NumPy?
346. How to insert a row at a specific location in a 2d array in NumPy?
347. How to repeat each element of a NumPy array 5 times?
348. What's the correct and efficient way to flatten NumPy array?
349. How to find element-wise maximum values from a NumPy array?
350. NumPy string functions like isalpha and isdigit
351. How to fix 'Why does the shape of a 1D array not show the number of rows as 1'?
352. How to wrap around slices in NumPy?
353. How to select one element in each row of a NumPy array by column indices?
354. How to change max in each row to 1, all other numbers to 0 in NumPy array?
355. How to find the first occurrence of subarray in NumPy array?
356. How to get the opposite diagonal of a NumPy array?
357. How to solve an equation using a NumPy numerical solver?
358. How to convert a column or row matrix to a diagonal matrix?
359. How to perform a reverse cumulative sum on a NumPy array?
360. How to take subarrays from NumPy array with given stride/stepsize?
361. How to remove zero lines from 2-D NumPy array?
362. How to check if a NumPy dtype is integral?
363. Specify a NumPy dtype when generating random values
364. Change the values of the diagonal of a NumPy matrix
365. How to invert a permutation array in NumPy?
366. 'AttributeError: rint' when using numpy.round()
367. Compute cross-correlation of two given NumPy arrays