CODEWITHSUNDEEP
pythondictionary
kms
kms

Reputation: 2024

Error when looking up max value from a python dictionary : max() arg is an empty sequence

I am trying to filter a dictionary and find the max from a list of values. Here a sample dictionary:

import numpy as np

def clean_currency(x):
""" If the value is a string, then remove currency symbol and delimiters
otherwise, the value is numeric and can be converted
"""
    if isinstance(x, str):
       return(x.replace('$', '').replace(',', ''))
    return(x)



d = {
     'shores': ['$0.00'],
     'Broderick': ['$0.00', '$0.00', '$0.00'],
     '100 Broderick': ['$0.00', '$1,142,070.00', '$0.00', '$0.00', '$0.00'],
     '1001 Orange Grove': ['$0.00'],
     '1008 Hyde': [np.nan]
    }


# Keep the highest value from the list. 

revd = {
        k: max((e for e in v if pd.notna(e)), key=lambda x: float(clean_currency(x)) if isinstance(x, str) else x)
        for k,v in d.items()
       }

revd

I am getting ValueError: max() arg is an empty sequence error.

Full traceback

ValueError                                Traceback (most recent call last)
/var/folders/d0/gnksqzwn2fn46fjgrkp6045c0000gn/T/ipykernel_49841/938463883.py in <module>
      1 # Keep the highest value from the list.
      2 
----> 3 revd = {
      4         k: max((e for e in v if pd.notna(e)), key=lambda x: float(clean_currency(x)) if isinstance(x, str) else x)
      5         for k,v in d.items()

/var/folders/d0/gnksqzwn2fn46fjgrkp6045c0000gn/T/ipykernel_49841/938463883.py in <dictcomp>(.0)
      2 
      3 revd = {
----> 4         k: max((e for e in v if pd.notna(e)), key=lambda x: float(clean_currency(x)) if isinstance(x, str) else x)
      5         for k,v in d.items()
      6        }

ValueError: max() arg is an empty sequence

Upvotes: 0

Views: 92

Answers (1)

juanpa.arrivillaga
juanpa.arrivillaga

Reputation: 95948

The problem is you are filtering all the nans out, leaving you with an empty sequence in some case. But there is no need to filter nans, as far as I can tell. The reasonable response for the maximum of all nans is nan, which is already the behavior you'd get, so just use something like this:

from pprint import pprint

def clean_currency(x):
    """ If the value is a string, then remove currency symbol and delimiters
    otherwise, the value is numeric and can be converted
    """
    if isinstance(x, str):
       x = x.replace('$', '').replace(',', '')
    return float(x)



d = {
     'shores': ['$0.00'],
     'Broderick': ['$0.00', '$0.00', '$0.00'],
     '100 Broderick': ['$0.00', '$1,142,070.00', '$0.00', '$0.00', '$0.00'],
     '1001 Orange Grove': ['$0.00'],
     '1008 Hyde': [float('nan')]
    }


# Keep the highest value from the list.

revd = {
    k: max(v, key=clean_currency)
    for k,v in d.items()
}

pprint(revd, sort_dicts=False)

which outputs:

{'shores': '$0.00',
 'Broderick': '$0.00',
 '100 Broderick': '$1,142,070.00',
 '1001 Orange Grove': '$0.00',
 '1008 Hyde': nan}

Upvotes: 1

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