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. Language Basics

Lesson 4. Variables

Variables in Python are fun.

Variables are data in programs that either change on the fly or are used to represent some value that you set once, and then use the variable in your code in place of that value.

Clearly variables are what make your program work.

Python is a strong and dynamically typed language. That is computer science talk for a language where the data types of variables do not change without explicit conversion (strongly typed), and that data type is decided at runtime (dynamically typed).

That is all well and good, but what all that really means is that you do not have to specify a data type for a variable when you declare it.

However, you do have to assign a variable a value when you create one. That initial variable definition is what decides the data type of the variable.

Examples

Simple Variable Declaration

cookies = 'nom nom nom'

print(cookies)

Using A Variable To Simplify Code

It is often the case that variables hold values that can be a bit unwieldy like file paths or URLs. In this case, we create a variable and assign it the unwieldy value so later in our code, we can use the simpler representation of the value.

import os

script_dir = os.getcwd()
rel_path = "data\\Eurostat.zip"
abs_file_path = os.path.join(script_dir, rel_path)

print(abs_file_path)

Changing The Value Of A Variable

Here is an example of changing the value of a variable.

i = 1

i = i + 1

print(i)

Now you try it!

Don't copy and past. Type the code yourself!

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Last updated 3 years ago