CODEWITHSUNDEEP
pandasdataframe
Ismael Ochoa
Ismael Ochoa

Reputation: 55

Repeat a set of rows (dataframe) and adding a string to each set

I have two DataFrames, one have all data to be repeated to create a new DataFrame but each time it is repeated, a column has to change its values using the letter from another DataFrame:

DF1 t1 t2 t3 t4 0 ABC 0 A 1950 1 CDE 1 A 1950 and DF2 [P,Q,R] I want to get:

DF0 t1 t2 t3 t4 0 ABC 0 A 1950-P 1 CDE 1 A 1950-P 2 XYZ 1 B 1954-Q 3 123 1 C 1954-Q 4 ABC 0 A 1950-R 5 CDE 1 A 1950-R

I have tried :

TMP = pd.DataFrame()
DF0 = pd.DataFrame()

TMP = DF1['t4']
DF1['t4'] = TMP + ' ' + DF2[0]
DF0 = DF0.append(DF1)

TMP = DF1['t4']
DF1['t4'] = TMP + ' ' + DF2[0]
DF0 = DF0.append(DF1)

but P is still in the second iteration and third, something like this:

1   CDE  1   A   1950-P
2   XYZ  1   B   1954-P-Q

Upvotes: 1

Views: 35

Answers (1)

jezrael
jezrael

Reputation: 862511

Use cross join with DataFrame.explode (pandas 0.25+) for repat lists values:

df2 = pd.DataFrame({'col':[['P','Q','R']]})
print (df2)
         col
0  [P, Q, R]

df2 = df2.explode('col')
print (df2)
  col
0   P
0   Q
0   R
df = df1.assign(a=1).merge(df2.assign(a=1), on='a')
df['t4'] = df['t4'].astype(str) + '-' + df['col']
print (df)
    t1  t2 t3      t4  a col
0  ABC   0  A  1950-P  1   P
1  ABC   0  A  1950-Q  1   Q
2  ABC   0  A  1950-R  1   R
3  CDE   1  A  1950-P  1   P
4  CDE   1  A  1950-Q  1   Q
5  CDE   1  A  1950-R  1   R

Upvotes: 1

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