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Activity for Karl Knechtelâ€
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Edit | Post #291768 |
Post edited: hide examples because they aren't strictly necessary to describe the problem; add some colour |
— | 6 months ago |
| Edit | Post #291769 |
Post edited: |
— | 6 months ago |
| Edit | Post #291769 | Initial revision | — | 6 months ago |
| Answer | — |
A: Why can't I use a library I just installed with Pip? Problems like this occur, fundamentally, because there is more than one Python installation on the system, and the system is configured in a way that `pip` installs for a different Python than the one that `python` runs. This problem can be addressed by either: using a virtual environment ru... (more) |
— | 6 months ago |
| Edit | Post #291768 | Initial revision | — | 6 months ago |
| Question | — |
Why can't I use a library I just installed with Pip? I tried installing `package-installation-test`[^1] using Pip, and it appeared to be successful. But I can't use it as advertised, either by itself or by importing it from my code: Failed attempts ```bash $ pip install package-installation-test Collecting package-installation-test Using c... (more) |
— | 6 months ago |
| Edit | Post #291757 | Initial revision | — | 6 months ago |
| Question | — |
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 environment with third-party libraries, figuring out an entry point for the code, and so forth. In parti... (more) |
— | 6 months ago |
| Comment | Post #291752 |
Oh, I was so busy making inter-related Q&As in my own style that I forgot about that one. I feel like this one should be considered a duplicate.... (more) |
— | 6 months ago |
| Edit | Post #291756 |
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| Edit | Post #291756 |
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| Edit | Post #291756 |
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| Edit | Post #291756 | Initial revision | — | 6 months ago |
| Answer | — |
A: Reinstall old Python libraries after update > Every time I run a program I'm used to, I get a bunch of import errors, and have to reinstall the dependencies. As you're presumably aware, the fundamental problem is that each Python installation is treated as its own separate environment, with its own suite of third-party libraries. Since ther... (more) |
— | 6 months ago |
| Comment | Post #291323 |
I guess you're aware, but I've split away content from this answer according to my plan now. If the downvote was yours, please feel free to re-evaluate. (more) |
— | 6 months ago |
| Edit | Post #291755 | Initial revision | — | 6 months ago |
| Answer | — |
A: How can I access and use command-line arguments in Python? At startup, Python loads the `sys` standard library module (without waiting for any code to `import` it) and sets up several useful values. Among these is sys.argv, which stores command-line arguments for the script. This is a plain list of strings, one per token on the command line (as in other prog... (more) |
— | 6 months ago |
| Comment | Post #291753 |
Thanks for the heads-up. I may come back and edit in some references to that. I do plan on having a separate Q&A later to cover the use of `__main__.py` as a module filename. (more) |
— | 6 months ago |
| Edit | Post #291753 |
Post edited: add link now that related question exists |
— | 6 months ago |
| Edit | Post #291754 | Initial revision | — | 6 months ago |
| Question | — |
How can I access and use command-line arguments in Python? In many other programming languages, the execution of code starts in a specifically named function (such as `main`) which is expected to have a specific signature, which allows that function to receive arguments from the command line. For example, we may write `int main(int argc, char argv)` in C ... (more) |
— | 6 months ago |
| Edit | Post #291753 | Initial revision | — | 6 months ago |
| Answer | — |
A: Understanding the `if __name__ == '__main__':` idiom Whenever Python loads code from a `.py` file, that code gets its own namespace for global variables - so they're not truly global, but per-file values. (When you look at an `import`ed module "from outside", those global variables are the attributes of the `module` object. Thus, when `module.py` has `... (more) |
— | 6 months ago |
| Edit | Post #291323 |
Post edited: move content about `if __name__ == '__main__':` to a new Q&A |
— | 6 months ago |
| Edit | Post #291752 | Initial revision | — | 6 months ago |
| Question | — |
Understanding the `if __name__ == '__main__':` idiom I've seen many examples of Python scripts that include a line that says: ```python if name == 'main': ``` Sometimes the following block contains a bunch of code, but other times it just makes a single function call (like `main()`), or some variant along the lines of ```python import sys ... (more) |
— | 6 months ago |
| Edit | Post #291748 | Initial revision | — | 6 months ago |
| Answer | — |
A: Regex to get text outside brackets First, we need to define some semantics. While it may not matter for your actual inputs, I propose that it should be valid for the output elements - the parts of the text found outside of brackets - to be empty strings. For example, if two bracketed parts are adjacent, like `onetwofour`, then a resul... (more) |
— | 6 months ago |
| Edit | Post #291676 |
Post edited: Shorten slightly by referring to newly created Q&A. (There is probably more redundancy that can be eliminated here.) |
— | 6 months ago |
| Edit | Post #291743 | Initial revision | — | 6 months ago |
| Answer | — |
A: Understanding Virtual Environments for Python Why The most important ideas behind virtual environments are: 1. Since there is a separate `site-packages`, you can isolate the dependencies of your project. This is especially important for testing and development, since you can more easily verify what your project's dependencies actually are.... (more) |
— | 6 months ago |
| Edit | Post #291616 |
Post edited: add tag |
— | 6 months ago |
| Edit | Post #291740 | Initial revision | — | 6 months ago |
| Question | — |
Understanding Virtual Environments for Python Several times now, I've seen advice in tutorials, setup/install instructions for Python-based projects, etc. to use a virtual environment to keep things organized and make it simpler to manage the code. It sounds like this means having yet another installation of Python on my computer. Does it rea... (more) |
— | 6 months ago |
| Comment | Post #291738 |
Of course it's entirely possible to set up an installer that installs both Python itself and your own Python code. There are even [tools to help with that](https://pynsist.readthedocs.io/en/latest/). But I wanted to focus this Q&A on approaches that involve a seamless user experience, where users don... (more) |
— | 6 months ago |
| Edit | Post #291739 |
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— | 6 months ago |
| Edit | Post #291739 |
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| Edit | Post #291739 | Initial revision | — | 6 months ago |
| Answer | — |
A: How can I make a standalone executable from Python code? Normally, Python is compiled, but it compiles to bytecode, not to your computer's native instructions. This bytecode is cross-platform, but it can't be used by the CPU directly - it can't be turned into a native executable. So fundamentally there are two ways to fix the problem: by using a custom ... (more) |
— | 6 months ago |
| Edit | Post #291738 | Initial revision | — | 6 months ago |
| Question | — |
How can I make a standalone executable from Python code? I know that I can make Python code run starting from the script, but this still requires the user to have Python installed (and will still rely on configuring the system so that it can find Python from the script, which can go wrong in a few different ways). I want to be able to distribute my prog... (more) |
— | 6 months ago |
| Edit | Post #291737 | Initial revision | — | 6 months ago |
| Answer | — |
A: How can I start my Python code, from the code itself? Mac/Linux In this environment, Python scripts can be given a shebang) line that tells the operating system that the file is a script, and what interpreter (i.e., Python) to use for it. Because `#` starts a comment in Python, Python itself doesn't need any special handling for this - it's just igno... (more) |
— | 6 months ago |
| Edit | Post #291736 | Initial revision | — | 6 months ago |
| Question | — |
How can I start my Python code, from the code itself? I have already learned how to tell the Python interpreter to run my code, but the standard approach feels a little unsatisfactory. I want the user experience to be that my program starts with the actual `.py` file, not with a Python interpreter. It's okay if a Python interpreter needs to be installed... (more) |
— | 6 months ago |
| Edit | Post #291323 |
Post edited: rm content that will be moved to a separate Q&A |
— | 6 months ago |
| Comment | Post #291708 |
I'm inclined to agree with John here. Numeric literals exist in programs for a wide variety of reasons, most of which are not engineering related. East Asian programmers typically don't use "localized" programming languages (these are a novelty at best anyway) but they do *comment* code in their nati... (more) |
— | 6 months ago |
| Edit | Post #291676 | Initial revision | — | 6 months ago |
| Answer | — |
A: Installing packages for, and using them with, a specific Python installation Choosing an environment for third-party libraries The short version of the answer is: Python installations don't normally share libraries because there are too many ways it could go wrong; generally each installation has its own install locations for third-party libraries; and generally each Pytho... (more) |
— | 6 months ago |
| Edit | Post #291675 | Initial revision | — | 6 months ago |