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(Stas Bekman) #535

Not if you do git pull. I have experienced this problem several times.

I think the best solution is to assert for a specific fasprogress version in the fastai code (and not just package dependencies). That way regardless of how people get their fastai updates, they will know right away that they need a newer version of fastprogress.

It doesn’t look this is common in python to perform that at the code level. Or at least I couldn’t find almost any references on how to do it, or even people asking about how to do it.

I found this suggestion:

import pkg_resources
import fastprogress

And if the version is insufficient, you’d get:

python -c 'import pkg_resources; pkg_resources.require("fastprogress>=0.1.19"); import fastprogress'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/stas/.local/lib/python3.6/site-packages/pkg_resources/", line 898, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/home/stas/.local/lib/python3.6/site-packages/pkg_resources/", line 789, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (fastprogress 0.1.18 (/home/stas/anaconda3/envs/pytorch-dev/lib/python3.6/site-packages), Requirement.parse('fastprogress>=0.1.19'))

(Stas Bekman) #536

fastai/environment.yml and environment-cpu.yml belong to the old fastai (0.7). conda env update is no longer the way to update your fastai-1.x environment. This is unfortunate, but we can’t remove these because the course-v2 video instructions rely on this setup. Eventually, once course-v3 p1 and p2 will be completed, they will probably be moved to where they belong - under old/.

instead do a normal install (even if you’re updating a previous install): conda install -c fastai fastai or pip install fastai and everything that needs to be updated will be updated.

It’s documented now here. Thank you for bringing up this issue, @ABertl.


Thanks for the help, I’ll try this out in the next few days.

To give some detail about what brought me to this point, I followed the recommendations of the MOOC and got a paperspace machine with preinstalled, and have been git pulling since with monthly-ish conda env update. (I eventually ran into the problem with nbextensions but really didn’t want to give it up!)

Somewhere in the middle of working my way through the MOOC I realized the lessons were being done with an old version of, and every time I was git pulling, none of the updates were hitting what I was using. Eventually I decided to try out 1.0.

I’m figuring it out, but it wasn’t real clear to me at first how to make the transition.

(Stas Bekman) #538

It can be very confusing indeed, especially given that fastai-0.7 files aren’t all in the same place, due to historic reasons I explained above. If you’re following the course-v2 MOOC you better stick to fastai-0.7, since the API has dramatically changed and it’ll be very difficult to make sense of the course-v2 videos using fastai-1.x. And if you do then, yes, you still need to use conda env update exactly as in the past. But you won’t need fastprogress then.

It wasn’t clear from your original post that you were referring to the fastai-0.7 version, but we do know that now. And if you do have installation issues with fastai-0.7 - please post those here.

(Stas Bekman) #539

I was curious to see if i could get to generate a train_ds w/ labels using the new API, but it appears to be very rough at the edges and failing in many ways if the prescribed way of train/valid split is not followed to the point, e.g.:

train_ds = ImageItemList.from_folder(path).random_split_by_pct(0)
IndexError: index 0 is out of bounds for axis 0 with size 0

and it also has an edge problem of generating 1 item in valid ds, which shouldn’t be there, since train ds, already has the full number of available items.

and this fails too:

train_ds = ImageItemList.from_folder(path)
train_ds = train_ds.label_from_folder()
TypeError: 'NoneType' object is not subscriptable

Is this a work-in-progress, or is the new API set to not allow any non-fastai-way of creating _ds objects (i.e. w/o valid set together with train_ds)?

I was experimenting with fashion mnist, but mnist will do too if you’d like to try it (i.e. path = /path/to/mnist)

I was planning to feed train_ds to ImageDataBunch.create(train_ds...) as in nbs/dl1/lesson7-wgan.ipynb, but the example there has no labels and w/o labels it works.

Thank you.

p.s. the 2 ways of using the test dataset w/ labels to validate against are now documented here.

(Jeremy Howard (Admin)) #540

Neither. It simply means you found a bug.

(RobG) #541

It looks like v1.0 has been released

(Stas Bekman) #542

FYI, @sgugger implemented this - so future git pull updates will be fastprogress-progress aware.

(Stas Bekman) #543

FYI, a hotfix fastai-1.0.36.post1 pypi release was made (a fix in regex dependencies which was conflicting with spacy)

And it looks like pip behaves strangely with .postX releases. When I first run:

pip install fastai

it won’t install fastai-1.0.36.post1 (installed fastai-1.0.34 instead, due to conflicts in 1.0.36 I suppose). But when I did:

pip uninstall fastai -y
pip install fastai

it did install fastai-1.0.36.post1. That’s a very inconsistent behavior.

(Kaspar Lund) #545

When using a network pretrained on imagenet then you must use image-netstat to normalise - always


On this, added a no_split method that will create a training set with everything and a validation set with nothing. Note that the empty validation set will still have a length of 1 otherwise the pytorch dataloader will complain (you have to test len(valid_ds.items) to check if it’s 0 or not.
Will change random_split_by_pct so that a 0 falls back to no_split, but this should be the method used.


Maybe-a-bit-breaking change: now that our transforms can pickle, DataBunch.export saves everything. That includes transforms and normalization, which means that you only have to type:

data = DataBunch.load_empty(path)

to get your empty data object ready for inference. Inference tutorial has been updated accordingly.

(Stas Bekman) #548

Comments on the tutorial updates:

“Now that our data has been properly set up, we can train a model. Once the time comes to deploy it for inference, we’ll need to save the information this DataBunch contains (classes for instance), to do this, we call data.export() . This will create an export.pkl file that you’ll need to copy with your model file if you want to deploy it on another device.”

Probably the best to show that in code, like the rest. That is it is explaining the instruction, but the instruction is not there.

empty_data = ImageDataBunch.load_empty(mnist)

I find the naming unintutive, how can it be empty if you called load on it?

(Stas Bekman) #549

Would it make it easier to code data blocks if each stage had a consistent prefix? like from_*, .label_*, etc?

Which would mean, renaming from:




I haven’t looked at all of it, but you get the idea.

If that resonates I’d be happy to compile the different options and propose renames to save you time.


To try to clarify the error messages that are encountered in fit/lr_find/show_batch because of a problem in the data, I’ve added an automatic sanity check of DataBunch after initialization. It can be disabled with no_check=True and will throw a warning if there is a problem to

  • access the elements of the training set
  • collate those elements in a batch

hopefully with an helpful error message.


New: support for one-hot encoded labels in multi-classification. The most basic way is to use MultiCategoryList with one_hot=True but if you label from a dataframe with multiple columns, the data block API will guess it’s a multiclass problem and put that flag for you.

(Pierre Ouannes) #553

Hey all ! It may be a very basic issue but I’ve looked on the forum, didn’t find anything and I’m really stuck.

I’m trying to get to get the fastai dev environment working in order to start to contribute to fastai (beginning by the documentation Sylvain asked for) but I’m having trouble setting it up. I followed the tutorial of the documentation and I’m at step 4 “write the code” (so I forked the repo, cloned it on my local computer, did pip install -e . and then tools/run-after-git-clone).
However when I try to run the first import cell of any notebook I get the following error :

File “/Users/bocra/anaconda3/lib/python3.5/site-packages/fastai/”, line 1, in
from .basic_train import *

File “/Users/bocra/anaconda3/lib/python3.5/site-packages/fastai/”, line 97
SyntaxError: invalid syntax

I think (but I’m not sure) it’s because fastai requires python >= 3.6 (pip install -e . told me so when I ran it). On the other hand, I installed fastai with the classic conda install and pytorch locked python at version 3.5 :

pytorch -> python[version=’>=3.5,<3.6.0a0’]

What am I missing ?

EDIT : And when I try to open an example notebook I get the following error :

Here’s the output of the terminal :

Adapting to protocol v5.1 for kernel 60c63f91-6415-4726-9b75-369756acfca7

(Kaspar Lund) #554

Hi seeing that the error refers to the conda enviroment i think you forgot to uninstall fastai.

First, follow the instructions above for either PyPi or Conda . Then uninstall the fastai package using the same package manager you used to install it, i.e. pip uninstall fastai or conda uninstall fastai , and then, replace it with a pip editable install.

git clone cd fastai tools/run-after-git-clone pip install -e .[dev]

(Pierre Ouannes) #555

Oops that’s right, a bad case of RTFM I guess, sorry about that.

Though to be fair I was following the instructions here and I think there’s an omission as there should be the uninstall step. I guess that’s going to be my first PR :wink:

Thank you very much !

(Mikhail Grankin) #556

I’m doing fp16 training. After training completes I call

learn.show_results(figsize=(12,15), rows = 10)

and I got and error

RuntimeError                              Traceback (most recent call last)
<ipython-input-21-cc1e87ad044f> in <module>()
----> 1 learn.show_results(figsize=(12,15), rows = 10)

~/anaconda3/lib/python3.7/site-packages/fastai/ in show_results(self, ds_type, rows, **kwargs)
    278         ds = self.dl(ds_type).dataset
    279         self.callbacks.append(RecordOnCPU())
--> 280         preds = self.pred_batch(ds_type)
    281         *self.callbacks,rec_cpu = self.callbacks
    282         x,y = rec_cpu.input,

~/anaconda3/lib/python3.7/site-packages/fastai/ in pred_batch(self, ds_type, batch)
    236         cb_handler = CallbackHandler(self.callbacks)
    237         cb_handler.on_batch_begin(xb,yb, train=False)
--> 238         preds = loss_batch(self.model.eval(), xb, yb, cb_handler=cb_handler)
    239         return _loss_func2activ(self.loss_func)(preds[0])

~/anaconda3/lib/python3.7/site-packages/fastai/ in loss_batch(model, xb, yb, loss_func, opt, cb_handler)
     16     if not is_listy(xb): xb = [xb]
     17     if not is_listy(yb): yb = [yb]
---> 18     out = model(*xb)
     19     out = cb_handler.on_loss_begin(out)

RuntimeError: Input type (torch.cuda.FloatTensor) and weight type (torch.cuda.HalfTensor) should be the same

from my understanding class MixedPrecision(Callback) sets the transformation on the start of training and then removes the transformation at the training end

class MixedPrecision(Callback):
    def on_train_begin(self, **kwargs:Any)->None:
        "Ensure everything is in half precision mode."
        if hasattr(, 'valid_dl') and is not None:
        if hasattr(, 'test_dl') and is not None:

   def on_train_end(self, **kwargs:Any)->None:
        "Remove half precision transforms added at `on_train_begin`."
        if hasattr(, 'valid_dl') and is not None:

So after the training there is no default transformation to fp16. I’d like to fix that if somebody will point towards where is the best place to put a fix.