Modifying dataFrames inside a list is not working

Question

I have two DataFrames and I want to perform the same list of cleaning ops. I realized I can merge into one, and to everything in one pass, but I am still curios

Answer 1

You are modifying copies of the dataframes rather than the original dataframes.

One way to deal with this issue is to use a dictionary. As a convenience, you can use pd.DataFrame.pipe together with dictionary comprehensions to modify your dictionaries.

def remove_nulls(df):
    return df[df['A'].notnull()]

dfs = dict(enumerate([test_1, test_2]))
dfs = {k: v.pipe(remove_nulls) for k, v in dfs.items()}

print(dfs)

# {0:    A   B
#     0  1  15
#     1  8  49
#     2  5  34
#     3  6  44
#     4  0  63,
#  1:      A    B
#     1  3.0  100
#     2  6.0  200
#     3  4.0  300
#     4  9.0  400
#     5  0.0  500}

Note: In your result dfs[1]['A'] remains float: this is because np.nan is considered float and we have not triggered a conversion to int.