savetxt two columns in python,numpy

Use numpy.c_[]:

np.savetxt('myfile.txt', np.c_[x, y, z])

Use numpy.transpose():

np.savetxt('myfile.txt', np.transpose([x, y, z]))

I find numpy.column_stack() most intuitive:

np.savetxt('myfile.txt', np.column_stack([x, y, z]))

Suggestion : 2

a list of specifiers, one per column - in this case, the real and imaginary part must have separate specifiers, e.g. [‘%.3e + %.3ej’, ‘(%.15e%+.15ej)’] for 2 columns,a full string specifying every real and imaginary part, e.g. ‘ %.4e %+.4ej %.4e %+.4ej %.4e %+.4ej’ for 3 columns,For e, E and f specifiers, the number of digits to print after the decimal point.,Minimum number of characters to be printed. The value is not truncated if it has more characters.

>>> x = y = z = np.arange(0.0, 5.0, 1.0) >>>
   np.savetxt('test.out', x, delimiter = ',') # X is an array >>>
   np.savetxt('test.out', (x, y, z)) # x, y, z equal sized 1 D arrays >>>
   np.savetxt('test.out', x, fmt = '%1.4e') # use exponential notation

Suggestion : 3

In this article we will discuss how to save 1D & 2D Numpy arrays in a CSV file with or without header and footer.,Python’s Numpy module provides a function to save numpy array to a txt file with custom delimiters and other custom options i.e. ,If you want to add comments in header and footer while saving the numpy array to csv file, then we can pass the header and footer parameters i.e. ,Let’s use this to save 1D and 2D numpy arrays to a csv file.

Python’s Numpy module provides a function to save numpy array to a txt file with custom delimiters and other custom options i.e.

numpy.savetxt(fname, arr, fmt = '%.18e', delimiter = ' ', newline = '\n', header = '', footer = '', comments = '# ', encoding = None)

First of all import Numpy module i.e.

import numpy as np

# Create a Numpy array from list of numbers
arr = np.array([6, 1, 4, 2, 18, 9, 3, 4, 2, 8, 11])

Let’s create a 2D numpy array from list of list i.e.

# Create a 2 D Numpy array list of list
arr2D = np.array([
   [11, 12, 13, 22],
   [21, 7, 23, 14],
   [31, 10, 33, 7]
])

# Save 2n d column of 2 D numpy array to csv file
np.savetxt('2darray_column.csv', [arr2D[: , 1]], delimiter = ',', fmt = '%d')

Suggestion : 4

Numpy Savetxt is a method to save an array to a text file or CSV file. In this coding tutorial, I will show you the implementation of the NumPy savetxt() method using the best examples I have compiled.,The above example was for one dimensional array. Now let’s save the two-dimensional array as a text and CSV file. Let’s create a Two Dimensional Array.,You can also save a Structured Numpy array to a CSV file. Those Numpy arrays that has a custom data type (dtype) is a structured Numpy array. Below is the code for the Structured Numpy array.,Data Science Library Computer Vision Data Preprocessing Data Science Foundation Statistics Probability Data Visualization Machine Learning NLP Numpy Pandas Python

First of all, let’s import all the necessary libraries required for this tutorial. Here I am using only NumPy library.

import numpy as np

2._

array_1d = np.array([10, 30, 40, 20])

Saving to text file

np.savetxt("array_1d.txt", array_1d, delimiter = ",")

You can also add a header and footer argument inside the np.savetxt() method. Just execute the following code.

np.savetxt("array_1d_with_hf.csv", [array_1d], delimiter = ",", fmt = "%d", header = "This is header", footer = "This is footer")

The above example was for one dimensional array. Now let’s save the two-dimensional array as a text and CSV file. Let’s create a Two Dimensional Array.

array_2d = np.array([
   [10, 30, 20],
   [60, 50, 40],
   [5, 6, 7]
])

Suggestion : 5

Last Updated : 13 Dec, 2018

Output :

x is: [0 1 2 3 4 5 6 7 8 9]
the file contains:
   0.000000000000000000e+00
1.000000000000000000e+00
2.000000000000000000e+00
3.000000000000000000e+00
4.000000000000000000e+00
5.000000000000000000e+00
6.000000000000000000e+00
7.000000000000000000e+00
8.000000000000000000e+00
9.000000000000000000e+00

Suggestion : 6

Second call the savetxt() method to append the rows.,Numpy savetxt to append to existing CSV file, Let us understand with the below example how to use Numpy savetxt() to append,We are using the NumPy module savetxt() method which allows us to save text and csv files.

numpy.savetxt(fname, X, fmt = '%.18e', delimiter = ' ', newline = '\n', header = '', footer = '', comments = '# ', encoding = None)

import numpy as np

List_rows = [
   ['Tom', 9, 8, 'WA'],
   ['Trex', 6, 15, 'CA'],
   ['Kity', 7, 11, 'WA']
]

list_row_append = [
   ['Rack', 9, 8, 'WA'],
   ['Sack', 6, 15, 'CA'],
   ['Mack', 7, 11, 'WA']
]

np_array_rows = np.array(List_rows)

np_array_rows_append = np.array(list_row_append)

with open('animal.csv', 'a') as csvfile:
   np.savetxt(csvfile, np_array_rows, delimiter = ',', header = 'Name, Age, Weight, City', fmt = '%s', comments = '')
np.savetxt(csvfile, np_array_rows_append, delimiter = ',', fmt = '%s', comments = '')

Name Age Weight City
Tom 9 8 WA
Trex 6 15 CA
Kity 7 11 WA
Rack 9 8 WA
Sack 6 15 CA
Mack 7 11 WA

import numpy as np

list_rows = [('Tom', 9, 8, 'WA'), ('Trex', 6, 15, 'CA'), ('Kity', 7, 11, 'WA')]
list_row_append = [('Rack', 9, 8, 'WA'), ('Sack', 6, 15, 'CA'), ('Mack', 7, 11, 'WA')]

dtype = [('Name', (np.str_, 10)), ('Marks', np.int32), ('weight', np.int32), ('City', (np.str_, 5))]

np_array = np.array(list_rows, dtype = dtype)

np_array_append = np.array(list_row_append, dtype = dtype)

with open('animal.csv', 'a') as csvfile:
   np.savetxt(csvfile, np_array, delimiter = ',', header = 'Name, Age, Weight, City', fmt = ['%s', '%f', '%d', '%s'], comments = '')
np.savetxt(csvfile, np_array_append, delimiter = ',', fmt = ['%s', '%f', '%d', '%s'], comments = '')

Name Marks Age city
Tom 9 8 WA
Trex 6 15 CA
Kity 7 11 WA
Rack 9 8 WA
Sack 6 15 CA
Mack 7 11 WA