python csv writer writes array in scientific notation

Question

I have a matrix of float numbers which i'm trying to write into a csv file, however csv writer writes it in scientific notation, i would like to leave the numbers in the original notation, i tried adding "%.2f" % but that resulted in the following error:

"TypeError: only length-1 arrays can be converted to Python scalars"

for item in string_color_Values:
   avg_color_values = [ float(item) for item in string_color_Values]

array1t = np.array(avg_color_values)
np.savetxt("test.csv", array1t, delimiter=",")

original:

 [ 0.5258  1.    ]
 [ 0.528   1.    ]
 [ 0.5486  1.    ]
 [ 0.5545  1.    ]
 [ 0.732   1.    ]
 [ 0.7872  1.    ]
 [ 1.      1.    ]]

Csv which i obtain:

1.2270000000035e-01,1.0000000000e+00
2.7639999999790e-01,1.0000000000e+00
etc..

Are you using numpy soley to write a CSV file? You should just use the csv module. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented May 1, 2017 at 5:11
Are you sure you have used the correct syntax: np.savetxt("test.csv", array1l, "%f.2", delimiter=",") works for me. — JohanL
– JohanL, Commented May 1, 2017 at 5:17

TimGJ · Accepted Answer · 2017-05-01 05:41:12Z

1

You need to have fmt="%g" in the call to np.savetxt. That will write the numbers without trailing zeroes. Alternatively if you want "cleanly" formatted nubmers you could use e.g. fmt="%.4f" (or any other format that takes your fancy).

import numpy as np
avg_color_Values = np.random.random((10,3))
array1t = np.array(avg_color_Values)
np.savetxt("test.csv", array1t, delimiter=",", fmt = "%g")

By default np.savetxt defaults to a format of %.18e, which will allows float64s to be written without loss of precicion.

answered May 1, 2017 at 5:41

TimGJ

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