Lesson 11

Grab data from multiple excel files and merge them into a single dataframe.

In [1]:
import pandas as pd
import matplotlib
import os
import sys
%matplotlib inline
In [2]:
print('Python version ' + sys.version)
print('Pandas version ' + pd.__version__)
print('Matplotlib version ' + matplotlib.__version__)
Python version 3.4.3 |Anaconda 2.4.0 (64-bit)| (default, Dec  1 2015, 11:39:45) [MSC v.1600 64 bit (AMD64)]
Pandas version 0.17.1
Matplotlib version 1.5.0

Create 3 excel files

In [3]:
# Create DataFrame
d = {'Channel':[1], 'Number':[255]}
df = pd.DataFrame(d)
df
Out[3]:
Channel Number
0 1 255
In [4]:
# Export to Excel

df.to_excel('test1.xlsx', sheet_name = 'test1', index = False)
df.to_excel('test2.xlsx', sheet_name = 'test2', index = False)
df.to_excel('test3.xlsx', sheet_name = 'test3', index = False)
print('Done')
Done

Place all three Excel files into a DataFrame

Get a list of file names but make sure there are no other excel files present in the folder.

In [5]:
# List to hold file names
FileNames = []

# Your path will be different, please modify the path below.
os.chdir(r"C:\Users\david\notebooks\pandas")

# Find any file that ends with ".xlsx"
for files in os.listdir("."):
    if files.endswith(".xlsx"):
        FileNames.append(files)
        
FileNames
Out[5]:
['test1.xlsx', 'test2.xlsx', 'test3.xlsx']

Create a function to process all of the excel files.

In [6]:
def GetFile(fnombre):

    # Path to excel file
    # Your path will be different, please modify the path below.
    location = r'C:\Users\david\notebooks\update\\' + fnombre
    
    # Parse the excel file
    # 0 = first sheet
    df = pd.read_excel(location, 0)
    
    # Tag record to file name
    df['File'] = fnombre
    
    # Make the "File" column the index of the df
    return df.set_index(['File'])

Go through each file name, create a dataframe, and add it to a list.

i.e.
df_list = [df, df, df]

In [7]:
# Create a list of dataframes
df_list = [GetFile(fname) for fname in FileNames]
df_list
Out[7]:
[            Channel  Number
 File                       
 test1.xlsx        1     255,             Channel  Number
 File                       
 test2.xlsx        1     255,             Channel  Number
 File                       
 test3.xlsx        1     255]
In [8]:
# Combine all of the dataframes into one
big_df = pd.concat(df_list)
big_df
Out[8]:
Channel Number
File
test1.xlsx 1 255
test2.xlsx 1 255
test3.xlsx 1 255
In [9]:
big_df.dtypes
Out[9]:
Channel    int64
Number     int64
dtype: object
In [10]:
# Plot it!
big_df['Channel'].plot.bar();

Author: David Rojas