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Questions tagged [yield-from]

"yield from" is an expression in Python for delegating to a subgenerator.

The expression yield from was added in Python-3.3 based on PEP 380: Syntax for Delegating to a Subgenerator.

In the simplest case it can be used as a shorthand for iterating over a subgenerator, i.e.

for item in sth:
    yield item

can be replaced with:

yield from sth
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How can I apply iter() to a pagination api?

I watched Raymond Hettinger's Idiomatic Python talk, and learned about the sentinel argument to iter(). I'd like to try to apply it to a piece of code I'm working on iterating over an API that uses pagination (it's Twilio, but not relevant to my…
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yield from a generator that has return statement in it

I have a generator with the return value statement in it. If i use next on it I get the Stopiteration: value from it as expected. However when I use yield from the value is lost. In [1]: def test(): ...: return 1 ...: yield 2 …
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Avoiding extra `next` call after `yield from` in Python generator

Please see the below snippet, run with Python 3.10: from collections.abc import Generator DUMP_DATA = 5, 6, 7 class DumpData(Exception): """Exception used to indicate to yield from DUMP_DATA.""" def sample_gen() -> Generator[int | None, int,…
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How to desugar a yield from syntax in Python?

Now I'm studying on the differences between a yield-from and an await syntax. From the official python documentation, the yield-from generator() is just a syntax suger of the following code: for i in generator(): yield i But I can't desugar the…
BrainVader
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Does CPython implement the mentioned optimizations from PEP 380?

PEP 380 mentions that the yield from expr syntax can be optimized in Python. PEP 380 - Optimizations Using a specialised syntax opens up possibilities for optimisation when there is a long chain of generators. Such chains can arise, for instance,…
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Concurrent download and processing of large files in python

I have a list of URLs for large files to download (e.g. compressed archives), which I want to process (e.g. decompress the archives). Both download and processing take a long time and processing is heavy on disk IO, so I want to have just one of…
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Mixing yield and return. `yield [cand]; return` vs `return [[cand]]`. Why do they lead to different output?

Why does yield [cand] return lead to different output/behavior than return [[cand]] Minimal viable example uses recursion the output of the version using yield [1]; return is different than the output of the version using return [[1]] def…
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How to yield objects recursively using python generator?

I am writing a generator function which recursively walks through all the child nodes for a given astroid node. In the example below, node is an astroid functiondef node. node.getchildren() returns a generator with subnodes in the node. My goal is…
Srijan Saurav
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Unable to Yield From inside async function and get yielded data

I am trying to Yield From a function from within an asynchronous function. Having spent hours trying to figure this out and traversing Stack Overflow to find similar questions previously answered but unable to help me find a solution to my own…
Michael Thompson
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Unsure of why the StopIteration isn't handled by "yield from"

Looking at the following sample code from the "Fluent Python" book that explains the "bidirectional tunnel" functionality of yield from, I have the following question. from collections import namedtuple Result = namedtuple('Result', 'count…
Noah Stebbins
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Breadth First Tree Traversal using Generators in Python

I am studying how to use Generators in Python in David Beazly's excellent Python Cookbook text. The following code recipe defines Depth First Tree Traversal using generators very elegantly: # example.py # # Example of depth-first search using a…
Bharat
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What does the expression "a = yield from f()" mean?

So, here is a python expression: a = yield from f() What does it mean? Where can it be used? What kind of object should f be? What will be the value of a after the expression is evaluated? There are several questions here on stackoverflow about…
lesnik
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Apply function for objects from "yield from" statement in python

# currently I have this code def some_func(): for match in re.finditer(regex, string): yield other_func(match) I was wondering if there was a way to squash it into one line # looking for something like def some_func(): yield from…
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How to understand `yield from` in python coroutine?

The code come form Fluent Python 1st edtion, I cannot understand the line while True: in grouper, delete that line raise a StopIteration error. But I find a new version of grouper without while True: that works. Why group.send(None) need another…
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How to save the output of recursive function to list of items using yield and generator functions

I have the following XML file from this link as sample: I have the following recursive function which prints output: import xml.etree.ElementTree as ET def perf_func(elem, func, level=0): func(elem,level) for child in elem.getchildren(): …
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