python - How can I replicate rows in Pandas?

Question

My pandas dataframe looks like this:

   Person  ID   ZipCode   Gender
0  12345   882  38182     Female
1  32917   271  88172     Male
2  18273   552  90291     Female

I want to replicate every row 3 times like:

   Person  ID   ZipCode   Gender
0  12345   882  38182     Female
0  12345   882  38182     Female
0  12345   882  38182     Female
1  32917   271  88172     Male
1  32917   271  88172     Male
1  32917   271  88172     Male
2  18273   552  90291     Female
2  18273   552  90291     Female
2  18273   552  90291     Female

And of course, reset the index so it is:

0
1
2
...

I tried solutions such as:

pd.concat([df[:5]]*3, ignore_index=True)

And:

df.reindex(np.repeat(df.index.values, df['ID']), method='ffill')

But none of them worked.

Answer 1

Use np.repeat:

Version 1:

Try using np.repeat:

newdf = pd.DataFrame(np.repeat(df.values, 3, axis=0))
newdf.columns = df.columns
print(newdf)

The above code will output:

  Person   ID ZipCode  Gender
0  12345  882   38182  Female
1  12345  882   38182  Female
2  12345  882   38182  Female
3  32917  271   88172    Male
4  32917  271   88172    Male
5  32917  271   88172    Male
6  18273  552   90291  Female
7  18273  552   90291  Female
8  18273  552   90291  Female

np.repeat repeats the values of df, 3 times.

Then we add the columns with assigning new_df.columns = df.columns.

Version 2:

You could also assign the column names in the first line, like below:

newdf = pd.DataFrame(np.repeat(df.values, 3, axis=0), columns=df.columns)
print(newdf)

The above code will also output:

  Person   ID ZipCode  Gender
0  12345  882   38182  Female
1  12345  882   38182  Female
2  12345  882   38182  Female
3  32917  271   88172    Male
4  32917  271   88172    Male
5  32917  271   88172    Male
6  18273  552   90291  Female
7  18273  552   90291  Female
8  18273  552   90291  Female