Tutorials
Hands-On Python
Hands-On Python
  • Hands-On Python Tutorial For Real-World Business Analytics Problems
  • Preface
    • Section I. A Note From The Author
    • Section II. Tutorial Overview
    • Section III. What Is The Preflight Checklist?
    • Section IV. Supplimentery Material
  • Preflight Checklist
    • Section V. Select Your Difficulty Setting
    • Section VI. Download Anaconda
    • Section VII. Download PyCharm (Optional)
    • Section VIII. Download SQL Server Developer Edition
    • Section IX. Configure Database Environment
    • Section X. Download The Source Code
    • Section XI. Starting JupyterLab
    • Section XII. How To Get Help With This Tutorial
  • Language Basics
    • Lesson 1. Obligatory Hello World
    • Lesson 2. Code Comments
    • Lesson 3. Data Types
    • Lesson 4. Variables
    • Lesson 5. String Concatenation
    • Lesson 6. Arithmetic Operators
    • Lesson 7. Making Decisions
    • Lesson 8. Control Flow With if-elif-else
    • Lesson 9. Control Flow With while
    • Lesson 10. Data Structures Part I: List
    • Lesson 11. Data Structures Part II: Tuples
    • Lesson 12. Data Structures Part III: Dictionaries
    • Lesson 13. Looping With for
    • Lesson 14. Functions
    • Lesson 15. Importing Modules
    • Lesson 16. Python Programming Standards
  • Advanced Topics
    • Lesson 17. Functional Programing With map
    • Lesson 18. Generators
    • Lesson 19. Comprehensions
    • Lesson 20. Basic File Operations
    • Lesson 21. Working With Data In Numpy
    • Lesson 22. Working With Data In Pandas
    • Lesson 23. Working With JSON
    • Lesson 24. Making File Request Over HTTP And SFTP
    • Lesson 25. Interacting With Databases
    • Lesson 26. Saving Objects With Pickle
    • Lesson 27. Error Handling
    • Lesson 28. Bringing It All Together
  • Solutions To Real World Problems
    • Lesson 29. Download A Zip File Over HTTP
    • Lesson 30. Looping Over Files In A Directory
    • Lesson 31. Convert Comma Delmited Files To Pipe Delimited
    • Lesson 32. Combining Multiple CSVs Into One File
    • Lesson 33. Load Large CSVs Into Data Warehouse Staging Tables
    • Lesson 34. Efficiently Write Large Database Query Results To Disk
    • Lesson 35. Working With SFTP In The Real World
    • Lesson 36. Executing Python From SQL Server Agent
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  1. Solutions To Real World Problems

Lesson 30. Looping Over Files In A Directory

Looping over files in a directory is a basic ETL task. In this tutorial, I’m going to introduce you to the syntax. If you downloaded the code from GitHub, there will be small sample files to work with.

In later lessons, you will see how it is done with live files.

Examples

Example #1: Loop Over Everything In Folder

import os

script_dir = os.getcwd()
data_directory = 'data\\'
example_directory = 'FileLoopExample\\'
path = os.path.join(script_dir,data_directory,example_directory)

for filename in os.listdir(path):
    print(filenamep

Example #2: Loop Over Files With A Specific File Extension

import os

script_dir = os.getcwd()
data_directory = 'data\\'
example_directory = 'FileLoopExample\\'
path = os.path.join(script_dir,data_directory,example_directory)

for filename in os.listdir(path):
    if filename.endswith('.csv'):
        print(filename

Example #3: Loop Over Files In Subdirectories Recursively

import os

script_dir = os.getcwd()
data_directory = 'data\\'
example_directory = 'FileLoopExample\\'
path = os.path.join(script_dir,data_directory,example_directory)

for subdir, dirs, files in os.walk(path):
     for filename in files:
            print(filename)
PreviousLesson 29. Download A Zip File Over HTTPNextLesson 31. Convert Comma Delmited Files To Pipe Delimited

Last updated 3 years ago