Re: Error installing matplotlib

On 03/09/2025 14:59, Mats Wichmann wrote:
> On 9/3/25 07:20, Rob Cliffe wrote:
>>
>>
>> On 03/09/2025 00:01, Mats Wichmann wrote:
>>> On 9/2/25 14:51, Rob Cliffe via Python-list wrote:
>>>>
>>> There are two roots here:
>>>
>>> (1) it's not finding a prebuilt wheel.  You can see that because 
>>> it's proposing to use the source distribution instead:
>>>
>>> > Collecting matplotlib
>>> >    Using cached matplotlib-3.10.6.tar.gz (34.8 MB)
>>>
>>> and so it, in the initial output.
>> I may be wrong, but I suspect that this is because I have attempted 
>> to do the install multiple times.  I.e. it didn't say this on the 
>> first run.
>>>
>>> (2) Although at this point all hope of success is often lost on 
>>> Windows, it's still going to try to compile things. It found gcc - 
>>> there are messages from g++ in the output. Last I know, Pybind11 
>>> only builds with the Microsoft compiler because it uses 
>>> msvc-specific types which gcc does not know about.
>>>
>>> Since the matplotlib project definition provides wheels for Python 
>>> 3.13 on Windows (not just the main Python, but also the 
>>> free-threaded versions), you need to figure out why the resolver 
>>> doesn't think there's anything applicable available.
>>>
>>>
>> Thanks for your reply, Mats, but I'm still lost.
>> Best wishes
>> Rob Cliffe
>
>
Thanks again Mats, I appreciate that you've done your best.
Sadly I have not been able to resolve the issue yet.
> I can't tell you specifically how to diagnose why it's not finding 
> what you hope it would find.  You might try these things:
>
> # remove cached entries so you're resolving all from PyPI
> pip cache purge
I tried this, it seems to make no difference.
>
> # do a test install with some flags that *might* give you useful info:
> pip -v install --dry-run --only-binary :all: --ignore-installed matplotlib
I'm not familiar with these pip options, but I tried this and got the 
following output:

Using pip 25.2 from C:\Python313\Lib\site-packages\pip (python 3.13)
ERROR: Could not find a version that satisfies the requirement 
matplotlib (from versions: none)
ERROR: No matching distribution found for matplotlib

>
>
> It would take people with more pip experience to dig deeper.
>
> I think the alternate manager "uv" may have more targeted debug 
> control for this scenario, but I don't promise, haven't used it that 
> much.
>
> I'm sure somebody will pop up with comments if this is bad advice - I 
> tried to answer the question of what's happening but not sure how to 
> fix it.

I am somewhat surprised (whinge, whinge 🙁) that I got this problem 
doing something completely normal
(installing a well-known package with a standard O/S and a standard 
version of Python).
Can anyone else help, please?
Best wishes
Rob Cliffe

-- 
https://mail.python.org/mailman3//lists/python-list.python.org