Python help

Hi @jeremy

I am exploring the source on _mk_param and use_kwargs_dic of fastcore, and like the idea of forcing Parameter to change kind from POSITIONAL_OR_KEYWORD to KEYWORD_ONLY. I think this may help to solve a tiny problem of fastcore.meta.delegates I noticed when exploring it.

The problem is presented in the first image below, and the solution learnt from _mk_param and use_kwargs_dict is in the second image.

What do you think of it? Thanks!

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That seems reasonable. Would you like to submit a PR with that change?

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Thanks Jeremy, I will give it try to submit a PR with it.

I tried PR but have a few issues and posted here.

I was curious what was going on here. Just sharing some articles I found useful:


Thanks for the sharing! They seem very helpful. I will look into them later.

At the moment, my nbdev project is broken and I can’t update the site for you to read the experiment I was doing. I will update the link here as soon as I fix it.

Hi Daniel, FYI The APL study nbdev project is also down. Jeremy is aware of this. So, don’t stress.


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Thank you so much Sarada! It’s so nice of you. I was feeling stressed about it.

However, I don’t know whether I am having the same issue though, as I can’t even do nbdev_preview.

Currently, I deleted my base and I am reinstall everything to see whether it solves my problem.

Reinstalling everything doesn’t solve the problem.

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When I am exploring FixSigMeta examples in fastcore.meta, I noticed a difference result:

The official 07_meta.ipynb has the example output as below:

But when I run the code, I got

Is it just my environment producing this different result?

I tried the code above on Kaggle and Try jupyter, and they give me different results too. And the reason for the difference is the python version.

I have pushed a PR, and I realised I need to make a few more changes to make the PR right

  1. I need to change my current python 3.9 to become fastcore’s python>=3.7
  2. remove the table of content of 07_meta.ipynb

Besides nbdev_prepare and nbdev_preview, should I run the 07_meta.ipynb to update all the outputs? When I check the PR for difference, there are many other files have been changed as a result, should I be worried about them?

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How to setup base environment and install fastai with python>=3.7?

The steps I took to setup everything are:
0. remove mambaforge folder

  1. bash Mambaforge-*.sh -b and ~/mambaforge/bin/conda init $SHELL_NAME
  2. mamba install -c fastchan fastai
    Note: up to this point, the python is version 3.9 in base env and 3.7 in ipython, and fastai is not available in ipython
  3. mamba install jupyter
    Note: up to this point, the python is version 3.9 in ipython too, and fastai is available in ipython
  4. mamba install -c fastai nbdev
  5. pip install jupyter_contrib_nbextensions

How do I get my python version to 3.7 for fastai and fastcore developement?

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Python 3.9 is >=3.7, so you don’t need to change that.

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If I don’t need to change the version of python, and the TOC has been removed, then what else should I do about the PR?

I’ve done a code review on it to let you know what’s needed.

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Thank you Jeremy! Your code review is very helpful, and I have shortened the code with your recommendation, and pushed again without rerunning all the cells so that it didn’t generate all the differences in cell outputs.

For total bigginer I recommend this course :
Everything is free and it is more practical than other bigger friendly courses.
I have flashcard for this book and some of python documentation. Feel free to contact me I will share it with you.However I put sometime way more stuff in one card than I should. (I did not obey flashcard rule).


If you ever read the source code of fastcore and have found concepts like metaclass, super, __new__, __call__ intimidating. The following tutorials should give you a good understanding to move on in reading the source, as they did for me.

Tutorials on metaclass

  • a lengthy and comprehensive one
  • a shorter and simpler one

A basic tutorial on static, class, instance, cls and self.

A tutorial on super

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How to print out a block of codes to the right of the line?

Here is the code I use to achieve the incorrectly aligned version. Could anyone help me to get the alignment right? Thanks

blocks = """
if to is None: 
    to_f,from_f = f.__base__.__init__,f.__init__
    to_f,from_f = to.__init__ if isinstance(to,type) else to,f
lst = blocks.split('\n')
for l in lst: 

The word “without” in description “2.” makes me unsure whether that is exactly the output you want, or if you are commenting how its not quite right. Two other interpretations could be: you want the “1.” code to keep its indentation but slide as far right as possible until the longest line hits the margin; or, you want all lines right-aligned as far as possible.

This is exactly what I want to achieve. Thanks for help clarify. I will try to be clearer next time.