Python-OGR: nested loop only loops once
Hiking & ActivitiesPython-OGR: Nested Loops Acting Up? Here’s Why (and How to Fix It!)
Ever been wrestling with geospatial data in Python, using OGR (that part of the GDAL library), and run into a weird problem where your nested loop only seems to loop once on the inside? Trust me, you’re not alone. It’s a super common head-scratcher, and it all boils down to how OGR handles reading features. Once you get the hang of it, though, it’s a pretty easy fix, and you’ll save yourself a ton of debugging.
The Culprit: OGR’s One-Way Ticket Through Features
Basically, OGR reads features from a layer in order, like reading a book page by page. It keeps track of where it is with an internal “read position.” So, when you loop through a layer using a for loop in Python, OGR moves that read position forward each time it grabs a feature. The gotcha? After the inner loop finishes its first full run, that read position is sitting right at the end of the layer. The next time the outer loop rolls around and the inner loop tries to start again, OGR’s already at the end of the line – nothing left to read! That’s why it only loops once.
Let’s look at a quick example:
python
You may also like
Disclaimer
Categories
- Climate & Climate Zones
- Data & Analysis
- Earth Science
- Energy & Resources
- Facts
- General Knowledge & Education
- Geology & Landform
- Hiking & Activities
- Historical Aspects
- Human Impact
- Modeling & Prediction
- Natural Environments
- Outdoor Gear
- Polar & Ice Regions
- Regional Specifics
- Review
- Safety & Hazards
- Software & Programming
- Space & Navigation
- Storage
- Water Bodies
- Weather & Forecasts
- Wildlife & Biology
New Posts
- Santimon Novelty Metal Wingtip Graffiti Breathable – Is It Worth Buying?
- WZYCWB Butterflies Double Layer Fishermans Suitable – Tested and Reviewed
- Cuero Loco Bull Neck Vaqueras – Review 2025
- Durango Westward: A Classic Western Boot with Modern Comfort? (Review)
- Retevis Earpiece Portable Charging Handsfree – Is It Worth Buying?
- Backpack Lightweight Insulated Organizers Christmas – Buying Guide
- Barefoot Chinese Landscape Painting Hiking – Review 2025
- Salomon LC1305900 AGILE 2 SET – Review 2025
- The Somme: A Hellish Stretch of Time in World War I
- KEEN Breathable Versatile Comfortable Outdoor – Tested and Reviewed
- Loungefly Academia Triple Pocket Backpack – Is It Worth Buying?
- The Somme: Victory or a Graveyard of Hope?
- Under Armour Standard Enduro Marine – Buying Guide
- LOWA Renegade Evo GTX Mid: Still a King on the Trail? (Review)