<?xml version="1.0" encoding="UTF-8"?><rss xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:atom="http://www.w3.org/2005/Atom" version="2.0"><channel><title><![CDATA[Topics tagged with python-typing]]></title><description><![CDATA[A list of topics that have been tagged with python-typing]]></description><link>https://community.secnto.com//tags/python-typing</link><generator>RSS for Node</generator><lastBuildDate>Mon, 08 Jun 2026 20:45:05 GMT</lastBuildDate><atom:link href="https://community.secnto.com//tags/python-typing.rss" rel="self" type="application/rss+xml"/><pubDate>Invalid Date</pubDate><ttl>60</ttl><item><title><![CDATA[Incompatible type in filter using a callable]]></title><description><![CDATA[@Engrnaveed-Saeed said in Incompatible type in filter using a callable:

“I’m encountering an issue where I get an ‘Incompatible type’ error when using a callable with filter(). The callable seems to work fine on its own, but when used within filter(), it throws this error. What could be causing this issue, and how can I resolve it?”

The “Incompatible type” error in filter() usually occurs when the callable you’re using doesn’t return a boolean value. The filter() function expects the callable to return True or False for each element, indicating whether that element should be included in the result.
Here are a few potential causes and solutions:

Callable Not Returning a Boolean

Ensure that the callable you’re passing to filter() returns a boolean value (True or False). For example:
# Incorrect: The function returns the value itself, not a boolean
def my_callable(x):
    return x

# Correct: The function returns a boolean condition
def my_callable(x):
    return x &gt; 0

result = filter(my_callable, [-2, -1, 0, 1, 2])
print(list(result))  # Output: [1, 2]


Incompatible Return Type

If your callable returns a non-boolean value (e.g., None, a string, or any other type), filter() will treat all non-None values as True but may still raise type errors if the value is not expected. For example:
# Incorrect: Returning a string (non-boolean)
def my_callable(x):
    return "valid" if x &gt; 0 else "invalid"

# Correct: Return boolean
def my_callable(x):
    return x &gt; 0


Using Lambda or Other Callables

Ensure that if you’re using a lambda or other callable types, they also return booleans:
# Correct usage with lambda
result = filter(lambda x: x % 2 == 0, [1, 2, 3, 4, 5])
print(list(result))  # Output: [2, 4]

Conclusion
To resolve the “Incompatible type” error in filter(), make sure your callable function returns a boolean (True or False) based on the condition that determines whether each item should be included in the result.
]]></description><link>https://community.secnto.com//topic/2680/incompatible-type-in-filter-using-a-callable</link><guid isPermaLink="true">https://community.secnto.com//topic/2680/incompatible-type-in-filter-using-a-callable</guid><dc:creator><![CDATA[zaasmi]]></dc:creator><pubDate>Invalid Date</pubDate></item></channel></rss>