How to decode a QR-code image in (preferably pure) Python?

Question

TL;DR: I need a way to decode a QR-code from an image file using (preferable pure) Python. I've got a jpg file with a QR-code which I want to decode using Python. I've found a couple libraries which claim to do this: PyQRCode (website here) which supposedly can decode qr codes from images by simply providing a path like this: ``` import sys, qrcode d = qrcode.Decoder() if d.decode('out.png'): print 'result: ' + d.result else: print 'error: ' + d.error ``` So I simply installed it using `sudo pip install pyqrcode`. The thing I find strange about the example code above however, is that it only imports `qrcode` (and not `pyqrcode` though) Since I think `qrcode` refers to this library which can only generate qr-code images it kind of confused me. So I tried the code above with both `pyqrcode` and `qrcode`, but both fail at the second line saying `AttributeError: 'module' object has no attribute 'Decoder'`. Furthermore, the website refers to Ubuntu 8.10 (which came out more than 6 years ag…

Accepted Answer

You can try the following steps and code using `qrtools`:

Create a `qrcode` file, if not already existing

- I used `pyqrcode` for doing this, which can be installed using `pip install pyqrcode`

And then use the code:

```
>>> import pyqrcode
>>> qr = pyqrcode.create("HORN O.K. PLEASE.")
>>> qr.png("horn.png", scale=6)
```

Decode an existing `qrcode` file using `qrtools`

- Install `qrtools` using `sudo apt-get install python-qrtools`

Now use the following code within your python prompt

```
>>> import qrtools
>>> qr = qrtools.QR()
>>> qr.decode("horn.png")
>>> print qr.data
u'HORN O.K. PLEASE.'
```

Here is the complete code in a single run:

```
In [2]: import pyqrcode
In [3]: qr = pyqrcode.create("HORN O.K. PLEASE.")
In [4]: qr.png("horn.png", scale=6)
In [5]: import qrtools
In [6]: qr = qrtools.QR()
In [7]: qr.decode("horn.png")
Out[7]: True
In [8]: print qr.data
HORN O.K. PLEASE.
```

Caveats

- You might need to install `PyPNG` using `pip install pypng` for using `pyqrcode`

In case you have `PIL` installed, you might get `IOError: decoder zip not available`. In that case, try uninstalling and reinstalling `PIL` using:

```
pip uninstall PIL
pip install PIL
```

If that doesn't work, try using `Pillow` instead

```
pip uninstall PIL
pip install pillow
```

How to decode a QR-code image in (preferably pure) Python?

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