Concatenate a list of pandas dataframes together

Question

I have a list of Pandas dataframes that I would like to combine into one Pandas dataframe. I am using Python 2.7.10 and Pandas 0.16.2

I created the list of datafram

Answer 1

concat also works nicely with a list comprehension pulled using the "loc" command against an existing dataframe

df = pd.read_csv('./data.csv') # ie; Dataframe pulled from csv file with a "userID" column

review_ids = ['1','2','3'] # ie; ID values to grab from DataFrame

# Gets rows in df where IDs match in the userID column and combines them 

dfa = pd.concat([df.loc[df['userID'] == x] for x in review_ids])

Answer 2

You also can do it with functional programming:

from functools import reduce
reduce(lambda df1, df2: df1.merge(df2, "outer"), mydfs)

Answer 3

If the dataframes DO NOT all have the same columns try the following:

df = pd.DataFrame.from_dict(map(dict,df_list))

Answer 4

Given that all the dataframes have the same columns, you can simply concat them:

import pandas as pd
df = pd.concat(list_of_dataframes)