Python Overview
Use this overview to connect Python's main ideas rather than memorising isolated method names. Values, control flow, functions, objects, and modules work together in a program.
Understand the idea
Start with the shape of the input and the result you need. Choose a container, separate transformations from side effects, and give error cases a defined outcome. A short pure function is easy to test before connecting it to files, user input, or a database. The example combines a function, a generator expression, and a clear filtering rule.
Where to try it
Open this example with Try in playground. The code loads as editable text and does not run until you select Run. The first run downloads Python. Each run starts fresh; temporary files created by a script are not files on your PC.
A worked example
def available_units(products):
return sum(product["stock"] for product in products if product["stock"] > 0)
print(available_units([{"stock": 0}, {"stock": 8}, {"stock": 3}]))
Read the result
The result is 11 units across products with positive stock.
Try one change
Test empty input and decide how a malformed record should be reported.