Building Robust Object-Oriented Python Applications and Libraries/

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Generator Expressions

Generator Expressions

Learn about the generator expressions with the help of an example.

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Overview

Sometimes we want to process a new sequence without pulling a new list, set, or dictionary into system memory. If we’re iterating over items one at a time, and don’t actually care about having a complete container (such as a list or dictionary) created, a container is a waste of memory. When processing one item at a time, we only need the current object available in memory at any one moment. But when we create a container, all the objects have to be stored in that container before we start processing them.

Example

For example, consider a program that processes log files. A very simple log might contain information in this format:

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Apr 05, 2021 20:03:29 DEBUG This is a debugging message.
Apr 05, 2021 20:03:41 INFO This is an information method.
Apr 05, 2021 20:03:53 WARNING This is a warning. It could be serious.
Apr 05, 2021 20:03:59 WARNING Another warning sent.
Apr 05, 2021 20:04:05 INFO Here's some information.
Apr 05, 2021 20:04:17 DEBUG Debug messages are only useful if you want
to figure something out.
Apr 05, 2021 20:04:29 INFO Information is usually harmless, but
helpful.
Apr 05, 2021 20:04:35 WARNING Warnings should be heeded.
Apr 05, 2021 20:04:41 WARNING Watch for warnings.

Log files for popular web servers, databases, or email servers can contain many gigabytes of data (one ...