Replacing dataframe row-element string inside a python dictionary

Question

I am trying to replace "-" by 'NA' for each dataframe which is inside a python dictionary, for this task I am using a for-loop, however it runs without error and doesn't perform the desired task

Code:

import pandas as pd

df1= pd.DataFrame(data={'col1': [1, 2, "-"], 'col2': [3, "-", 4]})
df2 = pd.DataFrame(data={'col3':[1,2,3,"-",5], 'col4':[1,2,'NA', '-', 'NA'], 'col5':['John', 'Mary', 'Gordon', 'Cynthia', 'Marianne']})
df3 = pd.DataFrame(data={'col6':[19, "-",20, 23]})

## dataframes dictionary ##

all_dataframes = {"df1": df1, "df2": df2, "df3": df3}

############################## removing "-"  #####################################

for k, v in all_dataframes.items():
    if v is '-':
        all_dataframes[k] = 'NA'

Output:

#{'df1':   col1 col2
# 0    1    3
# 1    2    -
# 2    -    4,
# 'df2':   col3 col4      col5
# 0    1    1      John
# 1    2    2      Mary
# 2    3   NA    Gordon
# 3    -    -   Cynthia
# 4    5   NA  Marianne,
# 'df3':   col6
# 0   19
# 1    -
# 2   20
# 3   23}

Expected Output:

#{'df1':   col1 col2
# 0    1    3
# 1    2    NA
# 2    NA    4,
# 'df2':   col3 col4      col5
# 0    1    1      John
# 1    2    2      Mary
# 2    3   NA    Gordon
# 3    NA    NA   Cynthia
# 4    5   NA  Marianne,
# 'df3':   col6
# 0   19
# 1    NA
# 2   20
# 3   23}

What could I adjust in the for-loop to accomplish the task?

Bennimi · Accepted Answer · 2021-01-25 23:36:24Z

1

It cannot work since v is a Dataframe, not an element of it. Supposing, you want to keep the procedure from above, try:

for k, v in all_dataframes.items():
     v.replace({'-': 'NaN'}, regex=True, inplace=True)
     #print(v)

Returns:

{'df1':   col1 col2
 0    1    3
 1    2  NaN
 2  NaN    4,
 'df2':   col3 col4      col5
 0    1    1      John
 1    2    2      Mary
 2    3   NA    Gordon
 3  NaN  NaN   Cynthia
 4    5   NA  Marianne,
 'df3':   col6
 0   19
 1  NaN
 2   20
 3   23}

edited Jan 25, 2021 at 23:36

answered Jan 25, 2021 at 23:29

Bennimi

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