When to use cla clf or close for clearing a plot in matplotlib

Question

Matplotlib offers these functions  cla       Clear axis clf       Clear figure close     Close a figure window  The documentation doesn t offer a lot of insight into what the difference between these functions is  When should I use each function and what exactly does it do

User · Answer

plt cla   means clear current axis  plt clf   means clear current figure  also  there s plt gca    get current axis  and plt gcf    get current figure   Read more here  Matplotlib  Pyplot  Pylab etc  What s the difference between these and when to use each

User · Answer

They all do different things  since matplotlib uses a hierarchical order in which a figure window contains a figure which may consist of many axes  Additionally  there are functions from the pyplot interface and there are methods on the Figure class  I will discuss both cases below   pyplot interface  pyplot is a module that collects a couple of functions that allow matplotlib to be used in a functional manner  I here assume that pyplot has been imported as import matplotlib pyplot as plt  In this case  there are three different commands that remove stuff   plt cla   clears an axes  i e  the currently active axes in the current figure  It leaves the other axes untouched   plt clf   clears the entire current figure with all its axes  but leaves the window opened  such that it may be reused for other plots   plt close   closes a window  which will be the current window  if not specified otherwise   Which functions suits you best depends thus on your use-case   The close   function furthermore allows one to specify which window should be closed  The argument can either be a number or name given to a window when it was created using figure number or name  or it can be a figure instance fig obtained  i e   usingfig   figure    If no argument is given to close    the currently active window will be closed  Furthermore  there is the syntax close  all    which closes all figures   methods of the Figure class  Additionally  the Figure class provides methods for clearing figures  I ll assume in the following that fig is an instance of a Figure   fig clf   clears the entire figure  This call is equivalent to plt clf   only if fig is the current figure   fig clear   is a synonym for fig clf    Note that even del fig will not close the associated figure window  As far as I know the only way to close a figure window is using plt close fig  as described above

User · Answer

There is just a caveat that I discovered today  If you have a function that is calling a plot a lot of times you better use plt close fig  instead of fig clf   somehow the first does not accumulate in memory  In short if memory is a concern use plt close fig   Although it seems that there are better ways  go to the end of this comment for relevant links    So the the following script will produce an empty list   for i in range 5       fig   plot figure       plt close fig    This returns a list with all figure numbers available print plt get fignums      Whereas this one will produce a list with five figures on it   for i in range 5       fig   plot figure       fig clf     This returns a list with all figure numbers available print plt get fignums      From the documentation above is not clear to me what is the difference between closing a figure and closing a window  Maybe that will clarify   If  you want to try a complete script there you have   import numpy as np import matplotlib pyplot as plt x   np arange 1000  y   np sin x   for i in range 5       fig   plt figure       ax   fig add subplot 1  1  1      ax plot x  y      plt close fig   print plt get fignums     for i in range 5       fig   plt figure       ax   fig add subplot 1  1  1      ax plot x  y      fig clf    print plt get fignums      If memory is a concern somebody already posted a work-around in SO see  Create a figure that is reference counted

[matplotlib] When to use cla(), clf() or close() for clearing a plot in matplotlib?

Examples related to matplotlib

Examples related to plot