面向对象的pyplot

Question

我需要处理 pyplot 对象，例如图形和轴。这是我想要的一个简化示例：

In [1]: import matplotlib.pyplot as mp

In [2]: fig = mp.figure()             # create a figure

In [3]: mp.show()                     # and immediately show it. And close.

In [4]: ax = fig.add_subplot(111)     # Then I create a plot on that figure

In [5]: ax.plot([1, 2, 3]) 
Out[5]: [<matplotlib.lines.Line2D at 0x104e29a50>]

In [6]: mp.get_fignums()              # But I already released the figure, so it doesn't appear in the list of available figures
Out[6]: []

In [7]: fig.axes[0].lines[0].get_data()   # The data is there, on the plot
Out[7]: (array([ 0.,  1.,  2.]), array([1, 2, 3]))

In [8]: mp.show()                     # But mp.show() shows nothing.

fig.show() 也不起作用。释放后如何显示图形？

UPD：有一个类似的问题：Matplotlib: re-open a closed figure?，但没有答案。

Answer 1

Which is the recommended way to plot: matplotlib or pylab? 问题与此问题相关。

pyplot 接口是一个便利模块，用于跟踪 a) 打开的图形和 b)“当前图形”和“当前轴”。下面是使用OO接口。

要拥有一个开放的图形并且能够在 repl 中输入新命令，您需要处于“交互”模式，该模式将 python repl 循环与 GUI 事件循环集成。

从您的问题看来，您使用的是 IPython，因此请使用 %matplotlib 魔法：

16:31 $ ipython
Python 3.5.1 |Continuum Analytics, Inc.| (default, Dec  7 2015, 11:16:01) 
Type "copyright", "credits" or "license" for more information.

IPython 4.2.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: %matplotlib
Using matplotlib backend: Qt4Agg

In [2]: import matplotlib.pyplot as plt

In [3]: fig, ax = plt.subplots()  # prompt returns immediatly leaving open figure

In [4]: ln, = ax.plot(range(15), label='test')  # draws line and updates figure

In [5]: ln.set_linewidth(5)  # changes lw and updates screen

In [6]: 

Answer 2

试试这个：

import matplotlib.pyplot as mp

fig = mp.figure()

plt.show() # empty figure appears, close it

fig = plt.gcf() # get current figure, this is the key piece.

ax = fig.add_subplot(111) # added axes object

ax.plot([1,2,3])

plt.show()

当我这样做时，我能够用绘制的对角线来显示情节。

Answer 3

我找到了！让我们创建一个 mp.Figure()

import matplotlib.pyplot as mp
fig = mp.Figure()

现在它没有连接到pyplot，所以我们不能显示它。这相当于关闭图形时发生的情况。您无法显示未连接到 pyplot 的图形这一事实已得到充分证明。试试看

In []: fig.show?
Docstring:
If using a GUI backend with pyplot, display the figure window.
For non-GUI backends, this does nothing.

（我减少了帮助消息的文本。） 但是有可能欺骗pyplot。让我们创建一个图形：

temp_fig = mp.figure()

从 temp_fig 中窃取图形管理器并将其分配给我们的 fig：

m = mp.get_current_fig_manager()
fig.canvas.manager = m

现在我们可以展示它了：

mp.show() # Shows the fig figure.

当然，删除 temp_fig 是个好习惯：

del temp_fig