Can I run Processing.org Python sketch from a Jupyter Notebook and pass data? - python

I was looking for a way to run "Processing in Python" scripts out of Jupyter notebooks so I installed calysto_processing. Then I discovered it wants to speak Javascript but I wanted to stay in Python. I want to launch and feed a sketch so the user can change the POV as the data loads, changes, etc.
import numpy as np
import processing as pg
aData = np.load("myDataFile",...)
sketch = pg.launch("mySketch")
while True:
sketch.update(aData.getNextBatch())

Related

Why do we need FuncAnimation?

In a Coursera class about plotting in Python with Matplotlib, I was taught to make animated plots by using a FuncAnimation object. Why is this necessary? The obvious technique would be to use a for loop that updates the plot and pauses on each iteration. That seems a lot easier.
I've tried this, and it didn't work. Here's a simple example:
import matplotlib.pyplot as plt
import numpy as np
import time
%matplotlib notebook
plt.plot([0, 1, 2], [0, 1, 0])
l = plt.gca().get_children()[0]
for i in range(5):
l.set_ydata([0, 1, i/10])
plt.show()
time.sleep(1)
The result is that only the final plot is shown, after a 5-second delay. Why doesn't this work?
EDIT: I should have specified that I'm running this code in a Jupyter notebook.
For general ways to animate matplotlib plots in jupyter notebook see Animation in iPython notebook.
It should hence be noted that the problem here only occurs when using the %matplotlib notebook backend in a jupyter notebook with a python loop instead of the internal matplotlib.animation classes.
In order to ensure interactivity, the %matplotlib notebook creates the matplotlib figure using its own little application inside the jupyter output. Before this application is started, one can of course not interact with it. And as soon as this application is started, the connection to the python code from the IPython notebook is necessarily lost. This behaviour is similar to other GUIs in python: Once the GUI event loop is started, the python code stops until the GUI is closed.

opencv.imshow will cause jupyter notebook crash

I check other question on google or stackoverflow, they are talking about run cv2.imshow in script, but my code run in jupyter notebook.
Here is my configuration:
ubuntu 16.4x64
python 3.5
opencv 3.1.0
I start a jupyter notebook: here is the code I put it notebook:
%pylab notebook
import cv2
cvim2disp = cv2.imread('data/home.jpg')
cv2.imshow('HelloWorld', cvim2disp)
cv2.waitKey() #image will not show until this is called
cv2.destroyWindow('HelloWorld') #make sure window closes cleanly
When I execute these code. image will show in a pop up window, but I can not close this window by clicking the x on the top right corner, and a moment later, system will prompt me that the window is not responding, it will give me 2 choices: "wait" , "fore quit". if I hit wait, then It will show the same prompt later, If I hit 'fore quit', then the jupyter notebook kernel die and I have to start over.
I google around, many solution suggest that I should add this code
cv2.startWindowThread()
before imshow, but situation get worse, the kernel hang forever!.
anybody have some idea what's going on.
Here is the pic of my error:
The API documentation for cv2.waitKey() notes the following:
This function is the only method in HighGUI that can fetch and handle events, so it needs to be called periodically for normal event processing unless HighGUI is used within an environment that takes care of event processing.
So perhaps calling the function in an endless loop would make the window responsive? I haven't tested this, but maybe you would like to try the following:
import cv2
cvim2disp = cv2.imread('data/home.jpg')
cv2.imshow('img', cvim2disp)
while(True):
k = cv2.waitKey(33)
if k == -1: # if no key was pressed, -1 is returned
continue
else:
break
cv2.destroyWindow('img')
I am not sure if you can open a window from Jupyter Notebook.
cv2.imshow expects a waitKey which doesn't work in Jupyter.
Here is what I have done (using OpenCV 3.3):
from IPython.display import display, HTML
import cv2
import base64
def imshow(name, imageArray):
_, png = cv2.imencode('.png', imageArray)
encoded = base64.b64encode(png)
return HTML(data='''<img alt="{0}" src="data:image/png;base64, {1}"/>'''.format(name, encoded.decode('ascii')))
img = cv2.imread('./media/baboon.jpg',cv2.IMREAD_COLOR)
imshow('baboon', img)
If you don't need to use cv2, just:
from IPython.display import Image
Image('./media/baboon.jpg')

PyDev Seaborn in Eclipse: “QPixmap: It is not safe to use pixmaps outside the GUI thread” on PyDev autocompletion popup

I'm getting the error
QPixmap: It is not safe to use pixmaps outside the GUI thread
when manually entering the following statements in Seaborn in the ipython-shell using PyDev in Eclipse:
import matplotlib.pyplot as mpl
import seaborn as sns
import pandas as pd
import numpy as np
# Turn interactive mode off:
mpl.ioff()
# Create some example Data:
df = pd.DataFrame({'A':np.random.rand(20),'B':np.random.rand(20)})
# Create seaborn PairGrid instance:
pg = sns.PairGrid(df)
At this point when I continue the last statement with a dot to e.g. chain a map()-method, like this:
pg = sns.PairGrid(df).
then Eclipse is trying to show a popup of all possible completions but that popup is immediatly getting closed and the console is getting filled with the aforementioned error, 42 lines of it to be precise.
I can continue and do this without problem:
gp = sns.PairGrid(df).map(mpl.scatter)
gp.fig.show()
And I get my plot just fine.
The same happens when doing sns.JointGrid(df.A,df.B). and sns.FacetGrid(df).
While playing around earlier I also got into situations where the console was actually killed by this error, I just can't replicate the steps that lead to this anymore.
Researching on this site it looked like it has to do with threading which I'm not using at all. Does Seaborn use it?
I want to create my plots by first creating a Grid/Figure and doing the plotting later, but this error suggests that this isn't a safe way to do things though the Seaborn doc says it's fine to do it like that:
https://seaborn.github.io/generated/seaborn.FacetGrid.html
EDIT:
When doing the same thing in Spyder I'm not getting the error but this warning when doing gp.fig.show():
C:\Anaconda2\lib\site-packages\matplotlib\figure.py:397: UserWarning:
matplotlib is currently using a non-GUI backend, so cannot show the figure
"matplotlib is currently using a non-GUI backend, "
When interactive mode is off I'm not seeing any graphic. With interactive mode on I'm still seeing the warning but get the graphic inline.
No popup in either case though. In Eclipse I'm getting both the error and the popup.
EDIT 2:
Running the whole thing as a script in Eclipse does not produce any error, only the manual entering like described above does.
I took a look at https://github.com/fabioz/Pydev/blob/master/plugins/org.python.pydev/pysrc/pydevconsole.py and the issue is that the code-completion on PyDev is being triggered in a secondary thread, not in the main (UI) thread.
I.e.: the code completion in the interactive console is not expecting that it'll touch code that'll actually interact with the gui.
For this to work, the completion command has to be queued for the main thread (as the regular commands are queued) and the thread has to wait for it to finish to then return its value.
Please report this as an issue in the PyDev tracker: https://www.brainwy.com/tracker/PyDev/ (i.e.: code-completion in the interactive console should happen in the UI thread).

Pyplot “cannot connect to X server localhost:10.0” despite ioff() and matplotlib.use('Agg')

I have a piece of code which gets called by a different function, carries out some calculations for me and then plots the output to a file. Seeing as the whole script can take a while to run for larger datasets and since I may want to analyse multiple datasets at a given time I start it in screen then disconnect and close my putty session and check back on it the next day. I am using Ubuntu 14.04. My code looks as follows (I have skipped the calculations):
import shelve
import os, sys, time
import numpy
import timeit
import logging
import csv
import itertools
import graph_tool.all as gt
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
plt.ioff()
#Do some calculations
print 'plotting indeg'
# Let's plot its in-degree distribution
in_hist = gt.vertex_hist(g, "in")
y = in_hist[0]
err = numpy.sqrt(in_hist[0])
err[err >= y] = y[err >= y] - 1e-2
plt.figure(figsize=(6,4))
plt.errorbar(in_hist[1][:-1], in_hist[0], fmt="o",
label="in")
plt.gca().set_yscale("log")
plt.gca().set_xscale("log")
plt.gca().set_ylim(0.8, 1e5)
plt.gca().set_xlim(0.8, 1e3)
plt.subplots_adjust(left=0.2, bottom=0.2)
plt.xlabel("$k_{in}$")
plt.ylabel("$NP(k_{in})$")
plt.tight_layout()
plt.savefig("in-deg-dist.png")
plt.close()
print 'plotting outdeg'
#Do some more stuff
The script runs perfectly happily until I get to the plotting commands. To try and get to the root of the problem I am currently running it in putty without screen and with no X11 applications. The ouput I get is the following:
plotting indeg
PuTTY X11 proxy: unable to connect to forwarded X server: Network error: Connection refused
: cannot connect to X server localhost:10.0
I presume this is caused by the code trying to open a window but I thought that by explicitely setting plt.off() that would be disabled. Since it wasn't I followed this thread (Generating matplotlib graphs without a running X server ) and specified the backend, but that didn't solve the problem either. Where might I be going wrong?
The calling function calls other functions too which also use matplotlib. These get called only after this one but during the import statement their dependecies get loaded. Seeing as they were loaded first they disabled the subsequent matplotlib.use('Agg') declaration. Moving that declaration to the main script has solved the problem.

how to display and close image in python?

I would like to display image in python and close it after user enters name of the image in terminal. I use PIL to display image, here is the code:
im = Image.open("image.jpg")
im.show()
My application display this image, but user task is to recognize object on image and write answer in terminal. If answer entered is correct user should get another image. Problem with PIL is that I cant close the image and with research the only sollution was to kill the process of image viewer, but this is not really reliable and elegant.
Are there any other libraries for displaying images that have methods like .show() and .close() ?
Just open any image viewer/editor in a separate process and kill it once user has answered your question e.g.
from PIL import Image
import subprocess
p = subprocess.Popen(["display", "/tmp/test.png"])
raw_input("Give a name for image:")
p.kill()
Terminal is meant to deal with linear command flow - meaning it asks a question, user answers, and then it can ask a different question. What you are trying to do here is for terminal to do two things, show an image and at the same time ask user a question. To do this you can do two of either things:
Multiprocessing
You can start a new thread/process and make PIL show the image using that thread, and meanwhile in the first thread/process ask a user a question. Then after the user answers, you can close the other thread/process. You can take a look at Python's threading module (link) for more information on how you can do that.
GUI
Instead of making your user interface in terminal, make a simple GUI application using whatever framework you are comfortable. I personally like PyQt4. Qt is very powerful GUI development toolkit and PyQt4 is a wrapper for it. If you make a GUI, then what you are tyring to do is rather trivial.
Might be an overkill, but for me the easiest and most robust solution was just to use matplotlib as it properly keeps track of the figures it creates, e.g. :
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
imgplot = plt.imshow(mpimg.imread('animal.png'))
plt.ion()
plt.show()
animal_name = raw_input("What is the name?: ")
plt.close()

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