pandas explode method for versions < 0.25.0

explode_method.txt

import numpy as np
values = df[column].tolist()
n = len(df[column].tolist())
counts = np.zeros(n, dtype='int64')    
for i in range(n):
    v = values[i]
    if len(v):
        counts[i] += len(v)
    else:
        # empty list-like, use a nan marker
        counts[i] += 1
        
result = np.empty(counts.sum(), dtype='object')
count = 0
for i in range(n):
    v = values[i]
    if len(v):
        for j in range(len(v)):
            result[count] = v[j]
            count += 1
    else:
        # empty list-like, use a nan marker
        result[count] = np.nan
        count += 1

from pandas.core.series import Series
rst = Series(result, index=df[column].index.repeat(counts),name = column_name)
df.drop([column_name], axis=1).join(rst).reindex(columns=df.columns, copy=False)