Capturing Output.ipynb
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Capturing Output With %%capture¶
IPython has a [cell magic](Cell Magics.ipynb), %%capture, which captures the stdout/stderr of a cell. With this magic you can discard these streams or store them in a variable.
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from __future__ import print_function
import sys
By default, %%capture discards these streams. This is a simple way to suppress unwanted output.
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%%capture
print('hi, stdout')
print('hi, stderr', file=sys.stderr)
If you specify a name, then stdout/stderr will be stored in an object in your namespace.
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%%capture captured
print('hi, stdout')
print('hi, stderr', file=sys.stderr)
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captured
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Calling the object writes the output to stdout/stderr as appropriate.
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captured()
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captured.stdout
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captured.stderr
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%%capture grabs all output types, not just stdout/stderr, so you can do plots and use IPython's display system inside %%capture
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%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np
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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, stderr or rich display, by passing --no-stdout, --no-stderr and --no-display
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%%capture cap --no-stderr
print('hi, stdout')
print("hello, stderr", file=sys.stderr)
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cap.stdout
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cap.stderr
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cap.outputs
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