print formatted numpy array

Question

I want to print formatted numpy array along with a float with different significant figures. Consider the following code

a = 3.14159
X = np.array([1.123, 4.456, 7.789])
print('a = %4.3f, X = %3.2f' % (a, X))
------------------------
TypeError: only size-1 arrays can be converted to Python scalars

I desire following output-

a = 3.141, X = [1.12, 4.45, 7.78]

Suggest a modification in the code.

you can't apply scalar %f formating to a whole array. As with a list you have to iterate, applying it element by element. — hpaulj
– hpaulj, Commented Aug 3, 2021 at 17:33

user_na · Accepted Answer · 2021-08-03 16:19:06Z

4

You can use np.set_printoptions(precision=2):

import numpy as np
a = 3.14159
X = np.array([1.123, 4.456, 7.789])
np.set_printoptions(precision=2)
print(f'{a = :4.3f}, X = {X}')

Output

a = 3.142, X = [1.12 4.46 7.79]

answered Aug 3, 2021 at 16:19

user_na

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Comments

akuiper · Accepted Answer · 2021-08-03 16:16:29Z

3

Convert array to string first with array2string:

print('a = %4.3f, X = %s' % (a, np.array2string(X, precision=2)))
# a = 3.142, X = [1.12 4.46 7.79]

answered Aug 3, 2021 at 16:16

akuiper

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2 Comments

SOFe Over a year ago

this doesn't have the commas as indicated in the question.

Tom Johnson Over a year ago

@SOFe np.array2string(X, precision=2, separator=',') would give you the commas. See the separator option in numpy.org/doc/stable/reference/generated/….

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