Capturing Output.ipynb
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Capturing Output with %%capture¶
One of IPython's new cell magics is %%capture, which captures stdout/err for a cell,
and discards them or stores them in variables in your namespace.
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import sys
By default, it just swallows it up. This is a simple way to suppress unwanted output.
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%%capture
print 'hi, stdout'
print >> sys.stderr, 'hi, stderr'
If you specify a name, then stdout and stderr will be stored in an object in your namespace.
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%%capture captured
print 'hi, stdout'
print >> sys.stderr, 'hi, stderr'
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captured
Calling the object writes the output to stdout/err as appropriate.
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captured()
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captured.stdout
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captured.stderr
%%capture only captures stdout/err, not displaypub, so you can still do plots and use the display protocol inside %%capture
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%pylab inline
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%%capture wontshutup
print "setting up X"
x = np.linspace(0,5,1000)
print "step 2: constructing y-data"
y = np.sin(x)
print "step 3: display info about y"
plt.plot(x,y)
print "okay, I'm done now"
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wontshutup()
And you can selectively disable capturing stdout or stderr by passing --no-stdout/err.
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%%capture cap --no-stderr
print 'hi, stdout'
print >> sys.stderr, "hello, stderr"
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cap.stdout
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cap.stderr
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