我如何将Python2中的file（）函数改编为Python3函数？

Question

Primary Issue

I am currently trying to run this particular Github Project on my Mac OS. It was most certainly coded for a system running Python 2. However, I am running Python3 and I need to make a few modifications to the program. Most of these modifications work seamlessly, except for the one below.

When I run the program with this command...

python3 separate_dsd.py -i ./../../Ricotti\ \&\ Alburquerque\ -\ Dont\ You\ Believe\ Me.mp3 -o ./ -m ./../../model1.pkl

...I get the error NameError: name 'file' is not defined . File has been replaced with io.open within Python3. However, simply replacing the function call with io.open is giving me an error.

The specific line is, f=file(filename,'rb') of the code block:

def load_model(filename):
    f=file(filename,'rb')
    params=pickle.load(f)
    f.close()
    return params

This resides in the file /DeepConvSep/examples/dsd100/separate_dsd.py . Now how would I go about replacing the exact behaviour of file(filename,'rb') with a io.open ?

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Responses to Answers Below

Currently I tried to follow @abarnert's suggestions and changed my code to:

def load_model(filename):
    with open(filename, 'rb') as f:
        return pickle.load(f)

But I still get the error:

Traceback (most recent call last):
  File "separate_dsd.py", line 336, in <module>
    main(sys.argv[1:])
  File "separate_dsd.py", line 333, in main
    train_auto(inputfile,outdir,model,0.3,30,25,32,513)
  File "separate_dsd.py", line 250, in train_auto
    params=load_model(model)
  File "separate_dsd.py", line 19, in load_model
    params=pickle.load(f)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xbb in position 2: ordinal not in range(128)

Answer 1

The file constructor was already discouraged in Python 2.5 (maybe even earlier) in favor of the open function. In Python 3, it was removed entirely. So, it should just be a matter of:

f=open(filename, 'rb')

Note that, unlike your second version, I did not remove the 'rb' "mode" argument. That b means "binary mode", and it's even more important in Python 3 than in Python 2. Without it, you're asking it to decode the file to Unicode text (using some default encoding), which isn't going to work with a binary file—it's going to give you something like the output in the second half of your question.

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As a side note, you may want to rewrite the function like this:

def load_model(filename):
    with open(filename, 'rb') as f:
        return pickle.load(f)

This guarantees that the file gets closed even if unpickling raises an exception.

Answer 2

It seems that you've got at least two options:

a) Replace the call to file() , with open() which is a built-in function in Python 3

b) Learn how to use the immensely helpful venv (virtual python environment) and create a runtime environment for this project using an instance of a Python 2 interpreter.

If you choose the former, you must specify that you're trying to read a binary file when you call open() :

open(filename, 'rb')

However, given that this is probably not the only instance, in this project, of an incompatibility between your Python 3 interpreter and the source code, I would suggest creating a Python 2 environment.