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numpy.savetxt()
  • Difficulty Level : Expert
  • Last Updated : 13 Dec, 2018

numpy.savetxt(fname, X, fmt='%.18e', delimiter=' ', newline='\n', header='', footer='', comments='# ', encoding=None) : This method is used to save an array to a text file.

Parameters:
fname : If the filename ends in .gz, the file is automatically saved in compressed gzip format. loadtxt understands gzipped files transparently.
X : [1D or 2D array_like] Data to be saved to a text file.
fmt : A single format (%10.5f), a sequence of formats, or a multi-format string, e.g. ‘Iteration %d – %10.5f’, in which case delimiter is ignored.
delimiter : String or character separating columns.
newline : String or character separating lines.
header : String that will be written at the beginning of the file.
footer : String that will be written at the end of the file.
comments : String that will be prepended to the header and footer strings, to mark them as comments. Default: ‘# ‘, as expected by e.g. numpy.loadtxt.
encoding : Encoding used to encode the output file. Does not apply to output streams. If the encoding is something other than ‘bytes’ or ‘latin1’ you will not be able to load the file in NumPy versions < 1.14. Default is ‘latin1’.

Code #1:




# Python program explaining  
# savetxt() function
import numpy as geek
  
x = geek.arange(0, 10, 1)
print("x is:")
print(x)
  
# X is an array
c = geek.savetxt('geekfile.txt', x, delimiter =', ')   
a = open("geekfile.txt", 'r')# open file in read mode
  
print("the file contains:")
print(a.read())

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

 
Code #2:




# Python program explaining  
# savetxt() function
  
import numpy as geek
  
x = geek.arange(0, 10, 1)
y = geek.arange(10, 20, 1)
z = geek.arange(20, 30, 1)
print("x is:")
print(x)
  
print("y is:")
print(y)
  
print("z is:")
print(z)
  
# x, y, z are 3 numpy arrays with same dimension 
c = geek.savetxt('geekfile.txt', (x, y, z)) 
a = open("geekfile.txt", 'r')# open file in read mode
  
print("the file contains:")
print(a.read())

Output :

x is:
[0 1 2 3 4 5 6 7 8 9]
y is:
[10 11 12 13 14 15 16 17 18 19]
z is:
[20 21 22 23 24 25 26 27 28 29]

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
1.000000000000000000e+01 1.100000000000000000e+01 1.200000000000000000e+01 1.300000000000000000e+01 1.400000000000000000e+01 1.500000000000000000e+01 1.600000000000000000e+01 1.700000000000000000e+01 1.800000000000000000e+01 1.900000000000000000e+01
2.000000000000000000e+01 2.100000000000000000e+01 2.200000000000000000e+01 2.300000000000000000e+01 2.400000000000000000e+01 2.500000000000000000e+01 2.600000000000000000e+01 2.700000000000000000e+01 2.800000000000000000e+01 2.900000000000000000e+01

 
Code #3: TypeError




# Python program explaining  
# savetxt() function
  
import numpy as geek
  
x = geek.arange(0, 10, 1)
y = geek.arange(0, 20, 1)
z = geek.arange(0, 30, 1)
print("x is:")
print(x)
  
print("y is:")
print(y)
  
print("z is:")
print(z)
  
# x, y, z are 3 numpy arrays without having same dimension 
c = geek.savetxt('geekfile.txt', (x, y, z)) 

Output:

fh.write(asbytes(format % tuple(row) + newline))
TypeError: only length-1 arrays can be converted to Python scalars

During handling of the above exception, another exception occurred:

% (str(X.dtype), format))
TypeError: Mismatch between array dtype (‘object’) and format specifier (‘%.18e’)

Note that if the numpy arrays are not of equal dimension error occurs.

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