How to duplicate a pandas dataframe to match other dataframe's length?

Question

Assume the following dataframes:

df1:

a    
10.
20.
30.
40.
50.
60.
70.
80.
90.
100.
110.
120.

df2:

b
1.
2.

df3:

b
1.
2.
3.

Knowing len(df1.values) % len(df2.values) == 0, I want to divide each element of df1 by each element of df2, after having repeated df2 as many times as needed to fit df11's length, meaning in this case

result(df1, df2):

a    
10.
10.
30.
20.
50.
30.
70.
40.
90.
50.
110.
60.

result(df1, df3):

a    
10.
10.
10.
40.
25.
20.
70.
40.
30.
100.
55.
40.

What is the cleanest way to achieve this, preferably without going through numpy?

Answer 1

Here's one way using np.resize, where the new array will be filled with copies of the original until it fits the specified length:

df1['a'] /= np.resize(df2.b.values, df1.shape[0])

      a
0    10.0
1    10.0
2    30.0
3    20.0
4    50.0
5    30.0
6    70.0
7    40.0
8    90.0
9    50.0
10  110.0
11   60.0

---

Or using pd.np.tile:

df1['a'] /= pd.np.tile(df2.b, df1.shape[0]//df2.shape[0])