runserver 命令的 PyCharm 问题

Question

I have a script, part of a Django app, that makes thumbnails from pdfs. I'm using the excellent wand package to do it: Here are the Wand docs

It runs fine if I do ./manage.py runserver from the command line, but if I run from PyCharm, it breaks.

When I step through the code, the problem is that the code used to open the blob always returns an empty wand.image object. It's the right class ( wand.image ) but it's an empty one. The object I pass it is a pdf, but the blob conversion, which produces no error at all, is empty.

The error occurs in the next line ( single_image = all_pages.sequence[0] ) because all_pages is empty, so the index is out of range.

Again, if I launch the server from the command line, it works, but if I launch from PyCharm, it breaks.

I'm using virtualenv.

Here's the code I'm running:

from wand.image import Image as WandImage
from wand.color import Color


def convert_to_thumb(pdf_path, slug):
    with open(pdf_path) as f:
        image_binary = f.read()
    all_pages = WandImage(blob=image_binary) #<-- Here image_binary is a pdf
    single_image = all_pages.sequence[0]     #<-- BOOM! all_pages is a wand.image, but it's empty. Gives an Index error
    with WandImage(single_image) as i:
        i.format = 'png'
        i.background_color = Color('white')  
        i.alpha_channel = 'remove'  
        i.transform(resize='x100')
        save_name = slug + '_pdf_preview.png'
        i.save(filename='/foo/bar/' + save_name)

        return i

EDIT: Here's some Debug info

When I run from CLI and use pdb.set_trace() to check the value of all_pages I get this

(Pdb) p all_pages
<wand.image.Image: 3da0549 'PDF' (612x792)>

But when I do the same thing from the PyCharm console, I get:

(Pdb) >? p all_pages
<wand.image.Image: (empty)>

The value of image_binary appears to be identical in both cases. I diffed them.

Furthermore, the value of libmagick (the ImageMagick install) is /usr/local/lib/libMagickWand.dylib in both cases.

EDIT: This is interesting. If I launch PyCharm from the system Terminal, it works fine.

EDIT: Added relevant run configuration settings

<configuration default="false" name="foo_bar_app" type="Python.DjangoServer" factoryName="Django server">
  <option name="INTERPRETER_OPTIONS" value="" />
  <option name="PARENT_ENVS" value="true" />
  <envs>
    <env name="PYTHONUNBUFFERED" value="1" />
    <env name="FOO_USERID" value="foobar" />
    <env name="DJANGO_SETTINGS_MODULE" value="foo_bar.settings" />
  </envs>
  <option name="SDK_HOME" value="$USER_HOME$/venv/foo_bar/bin/python" />
  <option name="WORKING_DIRECTORY" value="" />
  <option name="IS_MODULE_SDK" value="false" />
  <option name="ADD_CONTENT_ROOTS" value="true" />
  <option name="ADD_SOURCE_ROOTS" value="true" />
  <module name="foo_bar_app" />
  <option name="launchJavascriptDebuger" value="false" />
  <option name="port" value="8000" />
  <option name="host" value="" />
  <option name="additionalOptions" value="" />
  <option name="browserUrl" value="" />
  <option name="runTestServer" value="false" />
  <option name="runNoReload" value="false" />
  <option name="useCustomRunCommand" value="false" />
  <option name="customRunCommand" value="" />
  <RunnerSettings RunnerId="PyDebugRunner" />
  <RunnerSettings RunnerId="PythonCover" />
  <RunnerSettings RunnerId="PythonRunner" />
  <ConfigurationWrapper RunnerId="PyDebugRunner" />
  <ConfigurationWrapper RunnerId="PythonCover" />
  <ConfigurationWrapper RunnerId="PythonRunner" />
  <method />
</configuration>

Answer 1

EDIT: This is interesting. If I launch PyCharm from the system Terminal, it works fine.

Sounds like you are running PyCharm with different user permissions, when launching from the terminal.

Answer 2

i got this problem few month ago. The only way i found to fix it was to launch everything in admin mode. It's probably a permissions denied problem from system.

Answer 3

If you are referencing an image with a relative path this may be the expected behavior--an empty image--as the working directory will be different between terminal instances. Replace your file paths with absolute paths in your code.