Batch conversion of multiple numpy arrays into pandas DataFrames

Question

The following script converts multiple square matrices into pandas DataFrames, first manually, then as a loop function, plus labels their rows and columns identically.

import numpy as np
import pandas as pd
from numpy.random import rand

A1 = rand(3,3)
A2 = A1*2
A3 = A1*3 #example square matrices, no math pattern implied

labels = ['a','b','c']

Manual conversion:

A1 = pd.DataFrame(A1, index=labels, columns=labels)
A2 = pd.DataFrame(A2, index=labels, columns=labels)
A3 = pd.DataFrame(A2, index=labels, columns=labels)

Batch conversion (loop):

def batch_df(l):
    ll = []
    for A in l:
        A_ = pd.DataFrame(A, index=labels, columns=labels)
        ll.append(A_)
    return ll 

ll = batch_df([A1, A2, A3])
print(len(ll)) #list of unnamed matrices, but I would like them separately : A1, A2, ...

I would like to return the individual DataFrames separately instead, uniquely named, not bunched together in one list without names, but don't know how:

return A1, A2, A3

The function should be flexible enough to batch convert whatever number of arrays is passed into the function, not just 3

Dieter · Accepted Answer · 2021-01-10 13:21:45Z

1

   
   def batch_df(l):

       ...

       return ll

   # edit the expected return values
   A1, A2, A3 = batch_df([A1, A2, A3])

(i don't really understand your question)

or


import numpy as np
import pandas as pd
from numpy.random import rand

my_dfs = {}
my_dfs['A1'] = rand(3,3)
my_dfs['A2'] = my_dfs['A1'] * 2
my_dfs['A3'] = my_dfs['A1'] * 3 

labels = ['a','b','c']

#----------#
# Do stuff #
#----------#
def batch_df(d):
    
    # loop over the dataframes
    for k, A in d.items():
        # update the value
        my_dfs[k] = pd.DataFrame(A, index=labels, columns=labels)

     # no need to return --> dictionaries are by reference
        
        
batch_df(my_dfs)

res: my_dfs['A1']

    a           b           c
a   0.501693    0.506768    0.315132
b   0.382843    0.116506    0.194385
c   0.208627    0.033067    0.121261

edited Jan 10, 2021 at 13:21

answered Jan 10, 2021 at 12:52

Dieter

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7 Comments

develarist Over a year ago

ll in the question is a list. but inside that list are separate objects. making a function output ll by itself gives only one output. I instead would like to output 3 or more objects from the function, unpacked from the contents of ll

Dieter Over a year ago

but if you provide an equal amount of expected values --> A1, A2, A3 = <-- then there is no real issue?

Dieter Over a year ago

or that amount is unknown?

Dieter Over a year ago

Why don't you use, a dictionary?

develarist Over a year ago

the code before the edits worked fine, i was only replying to your question about not understanding

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