creating text file with multiple arrays of mixed types python

Question

I am trying to create a text file with multiple array as the columns in this file. The trick is that each array is a different datatype. For example:

a = np.zeros(100,dtype=np.int)+2 #integers all twos
b = QC_String = np.array(['NA']*100) #strings all 'NA'
c = np.ones(100,dtype=np.float)*99.9999 #floats all 99.9999

np.savetxt('filename.txt',[a,b,c],delimiter='\t')

However, I get an error:

TypeError: Mismatch between array dtype ('|S32') and format specifier   
('%.18e %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   %.18e   
%.18e')

Any ideas? Thanks!

N1B4 · Accepted Answer · 2016-07-18 21:03:25Z

2

I recommending using pandas to accomplish this task, which can easily handle multiple data types while writing out a new text file.

import numpy as np
import pandas as pd

# Create an empty DataFrame
df = pd.DataFrame()

# Populate columns in the dataframe with numpy arrays of different data types
df['a'] = np.zeros(100, dtype=np.int)+2
df['b'] = np.array(['NA']*100)
df['c'] = np.ones(100, dtype=np.float)*99.9999

# Store the data in a new text file
df.to_csv('./my_text_file.txt', index=False)

Opening up the .txt file reveals:

a,b,c
2,NA,99.999
2,NA,99.999
2,NA,99.999
...

answered Jul 18, 2016 at 21:03

N1B4

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5 Comments

HM14 Over a year ago

This seems great! Is there a way for it to be tab delimited instead of csv with this pandas method?

N1B4 Over a year ago

Yes, just add the sep='\t' argument during the write-out: df.to_csv('foo.txt', index=False, sep='\t')

HM14 Over a year ago

Ok so I think it is close, however I keep getting an error: ValueError: Length of values does not match length of index

N1B4 Over a year ago

Can you edit your post to show the code that you're running that produces this error?

HM14 Over a year ago

Ugh nevermind. I was working in Jupyter notebook and needed to restart my kernal. Thanks so much, it worked!

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