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I needed to make a plot using pandas and matplotlib. I am using python3.9 and tried the code in IPython. The matplotlib version is 3.3.2, and that of pandas 1.1.5. What I get, is unreadable text showed in the terminal with no plot being generated. Here is the code:

#Three lines to make the compiler able to draw:
 import sys
 import matplotlib
 matplotlib.use('Agg')

 import pandas as pd
 import matplotlib.pyplot as plt

 df = pd.read_csv('data.csv')

 df["Duration"].plot(kind = 'hist')

 plt.show()

 #Two  lines to make the compiler able to draw:
 plt.savefig(sys.stdout.buffer)
 sys.stdout.flush()

What is the reason behind ?

Improve this question
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    Something important is to call plt.savefig(...) before plt.show(), because as a side effect plt.show() erases the plot. Commented Jan 2, 2021 at 12:45
  • Thanks. Do I have to also call plt.savefig(...) at the end as I have done it ? An argument is required for the plt.savefig(...). What should I put as argument ? Commented Jan 2, 2021 at 13:53
  • 2
    To just display the plot, you normally only need plt.show(). plt.savefig(filename) is used to save a plot to a file. Where does the idea of using sys.stdout.buffer come from? Is it some really old code? Or are you using a very unusual environment? Commented Jan 2, 2021 at 13:57
  • 2
    What happens if you leave out matplotlib.use('Agg') (and restart the environment) to let matplotlib work with its defaults? If you are running jupyter, you may need %matplotlib inline (just an image) or %matplotlib notebook (interactive plot). See also here and here Commented Jan 2, 2021 at 14:21
  • I only need to see the plot and not save it to a file. I followed your suggestion. I got the plot saved in the working directory folder. When I omit the last two lines, I do not get the unreadable text I was complaining before. Thanks for your suggestion. If I do not save the plot via plt.savefig('filename'), the plot is not saved and not displayed. I only get the following message, which I also get if I save the plot: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure. Commented Jan 2, 2021 at 14:27
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