How to iterate each element of one data frame and compare the element with another data frame, then find probability of matching

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I have two example dataframes:

df1 = pd.DataFrame()
df1['a1'] = ['ABC','ACC','BCC','ABC']
df1['b1'] = ['ACC','AAC','BAC','ACC']

df2 = pd.DataFrame()
df2['a2'] = ['ACC','BCC','ABC']
df2['b2'] = ['AAC','BAC','ACC']
df2['types'] = [t1,t2,t3]
>>> df2
    a2   b2  types
0  ACC  AAC     t1
1  BCC  BAC     t2
2  ABC  ACC     t3

>>> df1
    a1   a2
0  ABC  ACC
1  ACC  AAC
2  BCC  BAC
3  CCC  CAC

I want to take a row from df1 and iterate through the df2 looking for matches. If a1 match a2 AND b1 match b2, then I want to count the type for calculating the probability of each type. For example, for the first row of df1, it matches the third row of df2, so I count t3 +1. I want to find an efficient way when there are more data

I tried:

for ind in df1:
    compare_item1= df1['a1'][ind]
    compare_item2 = df1['b1'][ind]
    for i in df2:
        count = 0
        if compare_item1 == df2['a2'][i] and compare_item2 == df2['b2'][i]:
            df1['t_{}'.format(i)]= count+1

what I thought is that for each iteration, create a dummy variables t_i and then I can do count and further calculations. However, I don’t get expected df1 with dummy variable. Any suggestion on how to fix it? Or any more efficient way to find probability?

Thanks!

pandas dataframe python
1 Answers

IIUC use:

df = df1.merge(df2, left_on=['a1','b1'], right_on=['a2','b2'])
    
print (df)
    a1   b1   a2   b2 types
0  ABC  ACC  ABC  ACC    t3
1  ABC  ACC  ABC  ACC    t3
2  ACC  AAC  ACC  AAC    t1
3  BCC  BAC  BCC  BAC    t2

df = df.groupby(['a1','b1','types']).size().reset_index(name='count')
print (df)
        a1   b1 types  count
0  ABC  ACC    t3      2
1  ACC  AAC    t1      1
2  BCC  BAC    t2      1
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