【matplotlib】 之 pyplot 中常用方法的源码调用过程（plt.plot、plt.scatter、plt.hist、plt.bar、plt.show、plt.savefig）
____tz_zs
关于这些方法的使用见 matplotlib 模块的简单使用 ，本文是关于这些方法在源码中的调用过程，用以加深对matplotlib库的理解。
plt.plot、plt.scatter、plt.hist、plt.bar 等
plt.plot、plt.scatter、plt.hist、plt.bar 等方法均调用 gcf() 获取 figure 对象，然后调用 figure 的 gca() 方法获取 axes 对象（如果没有 axes 则使用 self.add_subplot(1, 1, 1, **kwargs) 创建）。然后使用 axes.方法名 绘制相应的图。
1、调用同模块下的 ax = gca() 方法，获取 axes 对象。再使用 axes 绘制相应的图
pyplot.py
# This function was autogenerated by boilerplate.py. Do not edit as
# changes will be lost
@_autogen_docstring(Axes.plot)
def plot(*args, **kwargs):
ax = gca()
# Deprecated: allow callers to override the hold state
# by passing hold=True|False
washold = ax._hold
hold = kwargs.pop('hold', None)
if hold is not None:
ax._hold = hold
from matplotlib.cbook import mplDeprecation
warnings.warn("The 'hold' keyword argument is deprecated since 2.0.",
mplDeprecation)
try:
ret = ax.plot(*args, **kwargs)
finally:
ax._hold = washold
return ret.
2、gca 方法中 调用 gcf() 获取 figure 对象，并调用 figure 对象的 gca() 方法。
pyplot.py
def gca(**kwargs):
"""
Get the current :class:`~matplotlib.axes.Axes` instance on the
current figure matching the given keyword args, or create one.
Examples
--------
To get the current polar axes on the current figure::
plt.gca(projection='polar')
If the current axes doesn't exist, or isn't a polar one, the appropriate
axes will be created and then returned.
See Also
--------
matplotlib.figure.Figure.gca : The figure's gca method.
"""
return gcf().gca(**kwargs)pyplot.py
def gcf():
"""Get a reference to the current figure."""
figManager = _pylab_helpers.Gcf.get_active()
if figManager is not None:
return figManager.canvas.figure
else:
return figure().
3、figure 对象的 gca() 方法中，将返回 axes 对象。如果没有 axes 则会使用 self.add_subplot(1, 1, 1, **kwargs) 创建。
figure.py
class Figure(Artist):
"""
The Figure instance supports callbacks through a *callbacks*
attribute which is a :class:`matplotlib.cbook.CallbackRegistry`
instance. The events you can connect to are 'dpi_changed', and
the callback will be called with ``func(fig)`` where fig is the
:class:`Figure` instance.
*patch*
The figure patch is drawn by a
:class:`matplotlib.patches.Rectangle` instance
*suppressComposite*
For multiple figure images, the figure will make composite
images depending on the renderer option_image_nocomposite
function. If suppressComposite is True|False, this will
override the renderer.
"""
......
......
......
@docstring.dedent_interpd
def gca(self, **kwargs):
"""
Get the current axes, creating one if necessary
The following kwargs are supported for ensuring the returned axes
adheres to the given projection etc., and for axes creation if
the active axes does not exist:
%(Axes)s
"""
ckey, cax = self._axstack.current_key_axes()
# if there exists an axes on the stack see if it maches
# the desired axes configuration
if cax is not None:
# if no kwargs are given just return the current axes
# this is a convenience for gca() on axes such as polar etc.
if not kwargs:
return cax
# if the user has specified particular projection detail
# then build up a key which can represent this
else:
# we don't want to modify the original kwargs
# so take a copy so that we can do what we like to it
kwargs_copy = kwargs.copy()
projection_class, _, key = process_projection_requirements(
self, **kwargs_copy)
# let the returned axes have any gridspec by removing it from
# the key
ckey = ckey[1:]
key = key[1:]
# if the cax matches this key then return the axes, otherwise
# continue and a new axes will be created
if key == ckey and isinstance(cax, projection_class):
return cax
else:
warnings.warn('Requested projection is different from '
'current axis projection, creating new axis '
'with requested projection.', stacklevel=2)
# no axes found, so create one which spans the figure
return self.add_subplot(1, 1, 1, **kwargs).
plt.show
源码 pyplot.py
def show(*args, **kw):
"""
Display a figure.
When running in ipython with its pylab mode, display all
figures and return to the ipython prompt.
In non-interactive mode, display all figures and block until
the figures have been closed; in interactive mode it has no
effect unless figures were created prior to a change from
non-interactive to interactive mode (not recommended). In
that case it displays the figures but does not block.
A single experimental keyword argument, *block*, may be
set to True or False to override the blocking behavior
described above.
"""
global _show
return _show(*args, **kw)源码 pyplot.py
_show = pylab_setup()源码 backends/__init__.py
def pylab_setup(name=None):
'''return new_figure_manager, draw_if_interactive and show for pyplot
This provides the backend-specific functions that are used by
pyplot to abstract away the difference between interactive backends.
Parameters
----------
name : str, optional
The name of the backend to use. If `None`, falls back to
``matplotlib.get_backend()`` (which return ``rcParams['backend']``)
Returns
-------
backend_mod : module
The module which contains the backend of choice
new_figure_manager : function
Create a new figure manager (roughly maps to GUI window)
draw_if_interactive : function
Redraw the current figure if pyplot is interactive
show : function
Show (and possibly block) any unshown figures.
'''
......
......
......
return backend_mod, new_figure_manager, draw_if_interactive, show.
plt.savefig
保存当前 figure 为图片。
官网 matplotlib.pyplot.savefig
savefig(fname, dpi=None, facecolor='w', edgecolor='w',
orientation='portrait', papertype=None, format=None,
transparent=False, bbox_inches=None, pad_inches=0.1,
frameon=None)
参数：
fname : str 或者 file 对象，如果是 str 格式，文件的输出格式是根据 str 中的后缀决定的。如果字符串中没有后缀指定文件格式，则由 rc 参数 savefig.format 决定。
format ： str，文件格式，一般支持 png、pdf、ps、eps 和 svg。
示例：
#!/usr/bin/python2.7
# -*- coding: utf-8 -*-
"""
@author: tz_zs
"""
import numpy as np
import matplotlib.pyplot as plt
x = np.linspace(1, 100, 100)
y1 = np.random.randint(20, 60, size=100)
y2 = np.random.randint(30, 70, size=100)
y3 = np.random.randint(50, 90, size=100)
fig = plt.figure(num="111", figsize=(6, 4), facecolor="pink", edgecolor="green")
plt.plot(x, y1, c="red", label="y1_low")
plt.plot(x, y2, c="blue", label="y2_middle")
plt.plot(x, y3, c="yellow", label="y3_high")
plt.legend(loc="best")
# plt.show()
re = plt.savefig("a")
print(re)
"""
None
""".
源码调用过程：
获取当前 figure 的引用，然后调用 figure 对象的 savefig() 方法。
源码 pyplot.py
def gcf():
"""Get a reference to the current figure."""
figManager = _pylab_helpers.Gcf.get_active()
if figManager is not None:
return figManager.canvas.figure
else:
return figure()
......
......
......
@docstring.copy_dedent(Figure.savefig)
def savefig(*args, **kwargs):
fig = gcf()
res = fig.savefig(*args, **kwargs)
fig.canvas.draw_idle() # need this if 'transparent=True' to reset colors
return res
......
......
......figure.py
class Figure(Artist):
"""
The Figure instance supports callbacks through a *callbacks*
attribute which is a :class:`matplotlib.cbook.CallbackRegistry`
instance. The events you can connect to are 'dpi_changed', and
the callback will be called with ``func(fig)`` where fig is the
:class:`Figure` instance.
*patch*
The figure patch is drawn by a
:class:`matplotlib.patches.Rectangle` instance
*suppressComposite*
For multiple figure images, the figure will make composite
images depending on the renderer option_image_nocomposite
function. If suppressComposite is True|False, this will
override the renderer.
"""
......
......
......
def savefig(self, fname, **kwargs):
"""
Save the current figure.
"""
......
......
......
......
......
......
.
end