assign_other.py

bigSmallDict = (df['crime_category'].value_counts(normalize=True) > 0.05).to_dict()
# Make a dictionary saying if a category is > 5% of total or not

def assignOther(t):
    if bigSmallDict[t]: 
        return t
    else:
        return 'other'
# Define a mini function that looks in the dictionary

df['crime_category'] = df['crime_category'].apply(assignOther)
# Apply the function

df['crime_category'] = df['crime_category'].apply(lambda x: x if bigSmallDict[x] else 'other')
# As a one liner with an inline lambda function