为什么当pylab.show（）没有时，pylab.savefig（）会添加多个图，我如何使其停止？

Question

My program computes a number of diagrams, each with multiple plots. When executed using pylab.show() , it shows the first diagram in a window and when I close that window it shows the second diagram and so on, just fine.

When using pylab.savefig() , the second diagram contains both the plots from the first and the second diagram.

How do I keep savefig() from accumulating the plots?

This is the code I'm using to plot the diagrams:

# generate multiple plots for the first diagram
label = 4
for i in nylonLengthLists:  # take a list of lists to generate multiple plots
    pylab.plot(windSpeeds,i, label=str(label) + ' m')
    label += 1

pylab.title('Leinenlaengen nach Tiefen')
pylab.ylabel('Leinenlaenge (m)')
pylab.xlabel('Windgeschwindigkeit (kn)')
pylab.legend(loc='upper left', title='Tiefen')
pylab.xticks()

pylab.grid()
pylab.savefig('diagram1.png')

# generate the plots for the second diagram

nylonLengthLists = []    # reset and regenerate the list of lists
for i in range(12,25,2):
    nylonLengthLists.append(nylonLengthList(i, chainLength, boatLength)) 

label = 12
for i in nylonLengthLists:    # generate multiple plots
    pylab.plot(windSpeeds,i, label=str(label) + ' m')
    label += 2

pylab.title('Leinenlaengen nach Tiefen')
pylab.ylabel('Leinenlaenge (m)')
pylab.xlabel('Windgeschwindigkeit (kn)')
pylab.legend(loc='upper left', title='Tiefen')
pylab.xticks()

pylab.grid()
pylab.savefig('diagram2.png')

Answer 1

Closing a matplotlib window after a pylab.show destroys the figure instance. So a new one will be created at the next plotting command.

To get multiple figures without show , call pylab.figure each time you want to start a new plot.