Read complex numbers from a csv file using python

Question

I am having problem reading complex number from a csv file. The format of the file is the following:

( -353.10438 +j1.72317617 ),( -23.16000 +j0.72512251 )

I tried importing the data using numpy.genfromtxt:

data=genfromtxt(fname, dtype=complex, skip_header=10, skip_footer=212, delimiter=',')

But every time I have a complex entry it returns me nan+0.j. I also tried removing the brackets before and after the number, and replacing the j with 1j* but it didn't work.

Any suggestions? Thanks

Presumably you mean that you tried importing the data with genfromtxt? — Bill Bell
– Bill Bell, Commented Mar 21, 2017 at 13:13

Bill Bell · Accepted Answer · 2017-03-21 13:37:40Z

5

I moved each 'j' to the position immediately behind the imaginary part of the complex number and squeezed out all the blanks to get a sample file like this.

(-353.10438+1.72317617j),(-23.16000+0.72512251j)
(-353.10438+1.72317617j),(-23.16000+0.72512251j)
(-353.10438+1.72317617j),(-23.16000+0.72512251j)
(-353.10438+1.72317617j),(-23.16000+0.72512251j)

Then I ran code similar to yours with a result similar to what follows.

>>> np.genfromtxt('fname.txt', dtype=complex, delimiter=',')
array([[-353.10438+1.72317617j,  -23.16000+0.72512251j],
       [-353.10438+1.72317617j,  -23.16000+0.72512251j],
       [-353.10438+1.72317617j,  -23.16000+0.72512251j],
       [-353.10438+1.72317617j,  -23.16000+0.72512251j]])

I don't know exactly what you might have to do to get similar results, if indeed this approach will work for you at all.

Best of luck!

answered Mar 21, 2017 at 13:37

Bill Bell

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1 Comment

gian9 Over a year ago

I managed by doing how you said and eliminating the space before the +. Thanks!

rammelmueller · Accepted Answer · 2017-03-21 13:55:36Z

3

You can use

np.complex(str(a).replace('j', '') + 'j'

to first cast to a string, then shift the 'j' and cast back to a complex number.

edited Mar 21, 2017 at 13:55

answered Mar 21, 2017 at 13:40

rammelmueller

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2 Comments

gian9 Over a year ago

I used replace from the data directly. data=fname.read() and than data=data.replace() But I guess it's exactly the same as you said

rammelmueller Over a year ago

Yeah, the replace you can use whenever.. just before the actual parse to a complex number, since this must always be in the form "a+bj" in order to cast correctly.

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