Saving a 2d numpy array of strings with single array of different size to a csv file

Question

I have a 2D numpy array of strings. I am trying to save it to a CSV file. So, the issue comes when the sizes of 1D arrays are different.

For Example:

b = [['a','b']    #size of single array = 2
     ['c','d']]   #size of single array = 2

So, now if I try to save it using:

np.savetxt("filename.csv", b, fmt ="%s", delimiter=",")

The output csv file would be:

Col1      Col2     
-------    ----     
a          b        
c          d

Which is what I want, but now let's say I have a different sized 1D array.

For Example:

b = [['a','b']    #size of single array = 2
     ['c']]       #size of single array = 1

Now, when I try to save it, then the output file is:

Col1      Col2     
-------   ----     
['a'      'b']           
['c']

Whereas I want it to be saved as:

Col1       Col2     
-------    ----     
a          b        
c

Can someone help me out?

DmytroSytro · Accepted Answer · 2019-06-09 10:59:46Z

1

You can transform it to pandas dataframe first, than save to csv:

import pandas as pd

b = [['a','b'], ['c']]
df = pd.DataFrame(b)
df.fillna('', inplace=True)
df.to_csv(path)

But you asked about numpy array. If you have numpy array of lists, than you can transform it to list of lists first:

import numpy as np
import pandas as pd

b = np.array([['a','b'], ['c']])
b = list(b)
df = pd.DataFrame(b)
df.fillna('', inplace=True)
df.to_csv(path)

edited Jun 9, 2019 at 10:59

answered Jun 7, 2019 at 8:34

DmytroSytro

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2 Comments

Gopal Chitalia Over a year ago

Hey, thanks for the answer. But the converting to list of lists doesn't work. besides the pandas dataframe part, you are doing the same thing as my solution i.e. adjusting the length of the different sized list.

DmytroSytro Over a year ago

It works. What I meant is that your example isn't correct. You are asking about numpy array, but you are using list of lists in your example. Here you are creating list of lists in your example: b = [['a','b'],['c','d']]

Gopal Chitalia · Accepted Answer · 2019-06-07 08:23:14Z

0

Okay, since the issue is with different size of nested lists ( as np.savetxt works for same sized list ). I tried to make the size of all lists the same. And it worked.

I adjusted the length of all different sized 1D lists with the help of Question1 and Question2

If there's any other approach, please answer. It would be very useful

answered Jun 7, 2019 at 8:23

Gopal Chitalia

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