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Welcome to Software Development on Codidact!

Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.

Posts by Karl Knechtel‭

93 posts
88%
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Q&A What are statements and expressions?

When I have tried to read technical explanations of the syntax rules for programming languages, and when I am trying to decipher error messages, I often encounter the terms expression and statement...

4 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by Dirk Herrmann‭

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Meta How can we grow this community?

Never Too Late Due to, shall we say, recent AI-related hallucinations, pretty much everything that was possible PR-wise in 2019 is possible for this site again. People are leaving Stack Overflow a...

posted 1y ago by Karl Knechtel‭

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Q&A How can I build a string from smaller pieces?

Before attempting this, make sure it makes sense in context. In a few particular situations, it would be better to take a different approach rather than using the normal tools for composing or f...

posted 1y ago by Karl Knechtel‭  ·  edited 1y ago by Karl Knechtel‭

Answer
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Meta On self-answered questions, is it inappropriate to mark my own answer "Works for me" immediately?

Would it discourage others from posting answers, if they saw that a question had an answer with a "works for me" indication applied immediately? (More so than just seeing an immediate, comprehensiv...

3 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by matthewsnyder‭

84%
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Q&A Understanding mutable default arguments in Python

Consider this code example: def example(param=[]): param.append('value') print(param) When example is repeatedly called with an existing list, it repeatedly appends to the list, as ...

4 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 12mo ago by matthewsnyder‭

83%
+8 −0
Q&A Git-ignoring files with special characters in their names, especially newlines

My actual motivation is to understand the semantics of the .gitignore file syntax in precise detail, for a program which is expected to emulate them as accurately as possible. However, while coming...

1 answer  ·  posted 12mo ago by Karl Knechtel‭  ·  last activity 12mo ago by Peter Taylor‭

Question git linux gitignore
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Q&A Why are list comprehensions written differently if you use `else`?

These two uses of if are different The if at the end of a list comprehension syntax: [num for num in hand if num != 11] is a filter; its purpose is to decide whether or not the resulting list ...

posted 1y ago by Karl Knechtel‭  ·  edited 12mo ago by Karl Knechtel‭

Answer
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Q&A Understanding mutable default arguments in Python

Terminology "Mutable default argument" means exactly what the individual words would suggest: it's an argument which is supplied as the default value for that parameter, which also is mutable. To ...

posted 1y ago by Karl Knechtel‭  ·  edited 1y ago by Karl Knechtel‭

Answer
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Q&A How and where does Python code start running? How can I control that?

Suppose I have some code in a file myscript.py like: def my_function(): print("Test") What steps do I need to take in order to make my_function run? That is to say: how do I get Python to ...

2 answers  ·  posted 7mo ago by Karl Knechtel‭  ·  last activity 5mo ago by Michael‭

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Meta Don't close questions for lack of detail/confusion

No. Terms like "too generic", "unclear", "too broad", "off topic" are absolutely not euphemisms for "stupid question, go away". They mean what they say; and when they are used Somewhere Else, mult...

posted 8mo ago by Karl Knechtel‭

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Meta How should I organize material about text encoding in Python into questions?

I want to write one or more self-answered Q&As on the topic of text encoding in Python, to serve as canonicals and preempt future lower-quality questions. I can think of the following things th...

3 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by Karl Knechtel‭

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Q&A How can I properly type-hint methods in different files that would lead to circular imports?

Import modules rather than names first to avoid a circular reference in the import statements; then use forward declarations, as before, to avoid a circular reference in the type annotations - like...

posted 1y ago by Karl Knechtel‭  ·  edited 1y ago by Karl Knechtel‭

Answer
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Meta What categories could we benefit from having?

So far, existing Meta discussion seems to have at least hinted at the possibility of using separate categories here: To shuffle closed questions out of the way (globally for Codidact) (also) Fo...

1 answer  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by Lundin‭

77%
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Q&A How can I schedule a later task in Python?

Use at to schedule the command, using subprocess from Python to invoke at. It doesn't even require shell=True. For example: import shlex, subprocess subprocess.run( # `at` command to run n...

posted 1y ago by Karl Knechtel‭  ·  edited 1y ago by Karl Knechtel‭

Answer
77%
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Q&A Does Python have a "ternary operator" (conditional evaluation operator like "?:" in other languages)?

How to do it Yes, Python has an equivalent operator. However, it's spelled with keywords rather than punctuation, and it uses a different order of operands. It looks like: condition_value if some...

posted 12mo ago by Karl Knechtel‭

Answer
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Meta Is my question a duplicate? What now?

As part of a general effort to produce basic Q&As for Python, recently I've been focused on issues related to starting up an interpreter and running the code - so, questions about setting up an...

0 answers  ·  posted 5mo ago by Karl Knechtel‭

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Meta Do we want a wiki (or similar) alongside Q&A?

I think the framing of this question (and the prior discussion) is wrong, and I think that conditions have evolved since it was originally asked - in particular, we can now see how articles have tu...

posted 1y ago by Karl Knechtel‭  ·  edited 1y ago by Karl Knechtel‭

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Meta Should beginner-oriented Q&A here include basic use of a terminal (command line) for developers?

It seems that year over year, computers constantly get easier to use, and it becomes easier for people to start learning to program who have never touched it before. This comes with the consequence...

3 answers  ·  posted 5mo ago by Karl Knechtel‭  ·  last activity 5mo ago by matthewsnyder‭

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Q&A Why does `tkinter` (or `turtle`, or IDLE) seem to be missing or broken? Isn't it part of the standard library?

I had understood that Python is supposed to come "batteries included", and that the "batteries" specifically include: the tkinter standard library, a simple GUI framework a simple IDE cal...

1 answer  ·  posted 5mo ago by Karl Knechtel‭  ·  last activity 4mo ago by Karl Knechtel‭

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Q&A What actually is a pytest fixture?

The term long predates Pytest and is not at all specific to Python. The idea is described on Wikipedia: In the context of software a test fixture (also called "test context") is used to set up s...

posted 3mo ago by Karl Knechtel‭

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Q&A What does "namespace" mean?

A well-known easter egg in Python displays some ideas about writing good Python code, credited to Tim Peters (one of the core developers). This question is about the last: Namespaces are one hon...

2 answers  ·  posted 12mo ago by Karl Knechtel‭  ·  last activity 12mo ago by Olin Lathrop‭

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Q&A Understanding mutable default arguments in Python

Workarounds Avoiding mutation Because problems are only caused by actually mutating the default argument, the simplest way to avoid problems is to... not do that. Pythonic code obeys command-quer...

posted 1y ago by Karl Knechtel‭  ·  edited 12mo ago by Karl Knechtel‭

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Meta Should self-answered Q&A use separate answers for different techniques/approaches (even if there's a caveat that applies overall)?

Looking back at my own Q&A How can I build a string from smaller pieces?, the answer is incredibly long. I'm essentially showing five different ways to solve the problem - because they all exis...

2 answers  ·  posted 1y ago by Karl Knechtel‭  ·  last activity 1y ago by Lundin‭

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Meta Questions easily answered by studying a beginner-level book

There's still time This scenario is not yet a problem for this site, but we will get there, since it's a huge problem for Stack Overflow This topic should be separately addressed, too. At ti...

posted 1y ago by Karl Knechtel‭

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Q&A Choosing between multiple Python installations (environments) on the same computer

This answer assumes only installations of the reference "CPython" implementation, as provided by the official website at https://www.python.org. Other installations - such as those provided by th...

posted 6mo ago by Karl Knechtel‭  ·  edited 6mo ago by Karl Knechtel‭

Answer