create dictionary of dataframes via for loop

Question

I wish to create a dictionary of dataframes so I can pass into a function. Each dataframe is just a single line string.

Input:

test1=['1','2'] dn=['x','y'] Mag =['tet1','tet2'] pm=['1','2'] keys=[] final_list=[] df = pd.DataFrame() for num1 in test1: for num2 in dn: for num3 in Mag: for num4 in pm: keys.append(f'sw{num4}O{num1}{num2}{num3}') final_list.append(f'mp{num4}-ghfg{num1}-{num2}-{num3}') df=pd.DataFrame(final_list) df.append(df) d = {} d= dict(zip(keys, df))

Output:

In d['sw1O1xtet1']

Out 0

Desired Output: a dataframe containing the single line string 'mp1-ghfg1-x-tet1' corresponding to its key... NOt sure how to fix this...

You define df as a [] and next you use it as DataFrame - why? — balderman
– balderman, Commented Oct 5, 2020 at 9:50
my mistake as a beginner. I have changed it to df = pd.DataFrame(). Still investigating. — shoggananna
– shoggananna, Commented Oct 5, 2020 at 10:04

Arne · Accepted Answer · 2020-10-05 10:14:00Z

You can put each value in a dataframe before adding it to the dictionary. And you don't need the intermediate lists if you construct the dictionary directly by adding key-value pairs:

test1 = ['1', '2'] dn = ['x', 'y'] Mag = ['tet1', 'tet2'] pm = ['1', '2'] d = {} for num1 in test1: for num2 in dn: for num3 in Mag: for num4 in pm: key = f'sw{num4}O{num1}{num2}{num3}' value = pd.DataFrame({'col1': [f'mp{num4}-ghfg{num1}-{num2}-{num3}']}) d[key] = value

Dharman · Accepted Answer · 2020-10-05 10:00:13Z

The following code snippet will provide you the desired output.

import pandas as pd test1=['1','2'] dn=['x','y'] Mag =['tet1','tet2'] pm=['1','2'] keys=[] final_list=[] for num1 in test1: for num2 in dn: for num3 in Mag: for num4 in pm: keys.append(f'sw{num4}O{num1}{num2}{num3}') final_list.append(f'mp{num4}-ghfg{num1}-{num2}-{num3}') d = {} d = dict(zip(keys, final_list)) print(d['sw1O1xtet1'])

Thanks for your suggestion but unfortunately the constraint is that the output has to be a dafaframe containing this single line string

BrunoO · Accepted Answer · 2020-10-05 10:00:38Z

In order to understand what's wrong with your code, you can have a look at the result of zip

>>> [(a,b) for (a,b) in zip(keys, df)] [('sw1O1xtet1', 0)]

So you should not pass the whole dataframe to zip, only the first column df[0]

Also pay attention to the indentation, as the last 2 lines in the loop should be after the loop, not inside

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