How to assign string condition to a dataframe column condition?

Question

In a loop, I have built a string to be used as a column restriction in a panda dataframe :

conditions = pd.DataFrame()

for index, fold in df.iterrows():
    first_row = True
    for elem in fold['include_months']:
        if first_row: 
            condition = f"""('MonthNumber_"""+str(elem)+"' == 1)" 
            first_row = False
        else:
            condition += f""" | ('MonthNumber_"""+str(elem)+"' == 1)"

But I get an error with condition applied to panda column:

X_train = X_train[condition]

KeyError: "(X_train['MonthNumber_1'] == 1)| (X_train['MonthNumber_2'] == 1)"

How to fix it please?

Quang Hoang · Accepted Answer · 2022-06-11 19:41:03Z

1

Make condition not a string

condition = (X_train['MonthNumber_1'] == 1) | (X_train['MonthNumber_2'] == 1)

# since you're override your variable, it's best to make a copy
X_train = X_train[condition].copy()

You can also use query if you want to use a string form:

condition = 'MonthNumber_1 == 1 | MonthNumber_2 == 1'
X_train = X_train.query(condition).copy()

answered Jun 11, 2022 at 19:41

Quang Hoang

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2 Comments

Theo75 Over a year ago

Thanks but how to make condition not a string with :this code: train_months = f"""(X_train['MonthNumber_"""+str(elem)+"'] == 1)" ?

Quang Hoang Over a year ago

X_train.filter(like='MonthNumber').eq(1).any(axis=1).

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