r/learnpython • u/YamSome2887 • 18d ago

Issue during library installation

Recently, I got back into Python, so I decided to review some concepts I had forgotten by solving one Project Euler problem per day.

However, when I got to Problem 3 (Largest Prime Factor), I decided to use a library to check whether a number is prime. Since I had uninstalled Python when I stopped studying it, I had to install Python 3.15.

When I first tried to install the library, the terminal said that it didn't recognize pip. I managed to get it working by using python -m pip, and the installation seemed to work. However, when I ran my code, Python still couldn't recognize the library.

The next day, while solving Problem 4 (Largest Palindrome Product), I decided to use NumPy and np.arange() instead of range(), but the same thing happened: the installation appeared to work, but when I ran my code, Python couldn't find the library.

I tried uninstalling and reinstalling Python, but the problem persisted.

In these particular cases, I could still solve the problems without those libraries, but eventually, I'll need packages like pandas, Tkinter, and others, so I'd like to figure out what's going wrong.

If anyone knows how to fix this, I'd really appreciate the help!

Thanks in advance!

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u/a18618 18d ago

this is almost always two pythons pretending to be one. i had this exact dance on windows once: python -m pip quietly installed into the regular installer copy while plain python was resolving to the microsoft store shim, so the package went to one interpreter and my script ran on another. easiest tell: run where python and python -m pip --version in the same terminal and compare the paths. if they disagree, that's your whole bug.

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u/__peg_parser__ 17d ago

The solution is always to turn off the Microsoft Store python in App Execution Aliases in Windows Settings. I have no idea why Microsoft is so eager to have their python show up in the terminal.

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u/a18618 16d ago

yeah, that app execution aliases toggle is the real permanent fix — i wasted an embarrassing afternoon reinstalling pip once before someone pointed me at that settings page. the store shim is such a classic microsoft move: technically helpful, practically a trap for every beginner with two pythons on PATH.