python changes format numbers ndarray many digits

Question

I'm a beginner in python and easily get stucked and confused...

When I read a file which contains a table with numbers with digits, it reads it as an numpy.ndarray

Python is changing the display of the numbers. For example: In the input file i have this number: 56143.0254154 and in the output file the number is written as: 5.61430254e+04

but i want to keep the first format in the output file. i tried to use the string.format or locale.format functions but it doesn't work

Can anybody help me to do this?

Thanks! Ruxy

Could you give more context? How are you writing to the file for instance? — Jon Clements, Feb 06 '13 at 16:10

score 2 · Answer 1 · answered Feb 06 '13 at 16:43

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Try numpy.set_printoptions() -- there you can e.g. specify the number of digits that are printed and suppress the scientific notation. For example, numpy.set_printoptions(precision=8,suppress=True) will print 8 digits and no "...e+xx".

answered Feb 06 '13 at 16:43

Jan

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does this work when saving the array via `np.savetxt()`. thanks! – ryanjdillon Mar 31 '14 at 15:49
After testing, it looks like it doesn't. It is still necessary to set the format via `np.savetxt(... ,fmt='%f')` etc. Info on formatting can be [found here](http://docs.scipy.org/doc/numpy/reference/generated/numpy.savetxt.html). – ryanjdillon Mar 31 '14 at 17:55

Warren Weckesser · Answer 2 · 2017-07-24T15:35:52.547

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If you are printing a numpy array, you can control the format of the different data types by using the set_printoptions function. For example:

In [39]: a = array([56143.0254154, 1.234, 0.012345])

In [40]: print(a)
[  5.61430254e+04   1.23400000e+00   1.23450000e-02]

In [41]: set_printoptions(formatter=dict(float=lambda t: "%14.7f" % t))

In [42]: print(a)
[ 56143.0254154      1.2340000      0.0123450]

edited Jul 24 '17 at 15:35

answered Feb 06 '13 at 16:44

Warren Weckesser

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score 0 · Answer 3 · answered Feb 06 '13 at 16:44

You must create a formatted string. Assuming variable number contains the number you want to print, in Python 2.7 or 3, you could use

print("{:20.7f}".format(number))

whereas in Python 2:

print "%20.7f" % number

Alternatively, if you use Numpy routines to write out the array, use the method suggested by Warren.

python changes format numbers ndarray many digits

3 Answers3