Merging several pandas dataframes with different sizes

Question

My dataframe looks like this:

    007538839
0   105586.180
1   105582.910
2   105585.230
3   105576.445
4   105580.016

df1.shape = (69302, 1)

This has only one column with name "007538839". And I have several others dataframes that also has one column like this but with different column names and different row sizes.

    007543167
0   39886.620
1   39908.777
2   39886.574
3   39884.340
4   39871.098

df2.shape = (69778, 1)

I want to merge all of them together in a loop that looks like this:

import os
base_dir = ''
for root, dirs, files in os.walk(base_dir, topdown=False):
  for name in files:
    if root.count(os.sep) == 3 and name.endswith(".csv"):
       file_path = os.path.join(root, name)
       #merge all files

My goal is to not delete any rows, and for rows that do not yet have a value, NaN would be assigned. So for example, if I merge df1 and df2 I should get something with 69778 rows.

Answer 1

Create list of dictionaries first by append and then use concat with axis=1 :

import os
dfs = []
base_dir = ''
for root, dirs, files in os.walk(base_dir, topdown=False):
  for name in files:
    if root.count(os.sep) == 3 and name.endswith(".csv"):
       file_path = os.path.join(root, name)
       df = pd.read_csv(file_path)
       dfs.append(df)

df = pd.concat(dfs, axis=1)