Pandas column of lists, create a row for each list element

Question

I have a dataframe where some cells contain lists of multiple values. Rather than storing multiple values in a cell, I\'d like to expand the dataframe so that each item in t

Answer 1

Very late answer but I want to add this:

A fast solution using vanilla Python that also takes care of the sample_num column in OP's example. On my own large dataset with over 10 million rows and a result with 28 million rows this only takes about 38 seconds. The accepted solution completely breaks down with that amount of data and leads to a memory error on my system that has 128GB of RAM.

df = df.reset_index(drop=True)
lstcol = df.lstcol.values
lstcollist = []
indexlist = []
countlist = []
for ii in range(len(lstcol)):
    lstcollist.extend(lstcol[ii])
    indexlist.extend([ii]*len(lstcol[ii]))
    countlist.extend([jj for jj in range(len(lstcol[ii]))])
df = pd.merge(df.drop("lstcol",axis=1),pd.DataFrame({"lstcol":lstcollist,"lstcol_num":countlist},
index=indexlist),left_index=True,right_index=True).reset_index(drop=True)