我非常希望在matplotlibs 的Artist Class 中有一个copy 方法！
也许，有人想将下面的代码改编成Artist Class，以便有一种transfer 方法将一个Artist 对象复制到另一个对象中。
走错路了
对包copy 中的对象使用标准copy 或deepcopy 函数不起作用。
例如，编写脚本是没有用的：
import matplotlib.pyplot as plt
import numpy as np
import copy
x = np.linspace(0, 2*np.pi, 100)
fig = plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212)
# create a Line2D object
line1, = ax1.plot(x, np.sin(x))
# copy the Line2D object
line2 = copy.deepcopy(line1) #ERROR!
解决方案：
因此，我发现复制Artist 对象的唯一方法是创建所需类型的空对象，然后通过循环将原始对象中的所有必要属性转移到新创建的对象中。
将属性值从一个对象传输到另一个对象的工具是我定义的这个函数：
# -- Function to attributes copy
#It copies the attributes given in attr_list (a sequence of the attributes names as
# strings) from the object 'obj1' into the object 'obj2'
#It should work for any objects as long as the attributes are accessible by
# 'get_attribute' and 'set_attribute' methods.
def copy_attributes(obj2, obj1, attr_list):
for i_attribute in attr_list:
getattr(obj2, 'set_' + i_attribute)( getattr(obj1, 'get_' + i_attribute)() )
在这个函数中最重要的参数是attr_list。这是我们要从obj1 复制到obj2 的属性名称列表，例如，对于Artist.Line2D 对象，它可以是attr_list = ('xdata', 'ydata', 'animated', 'antialiased', 'color', 'dash_capstyle', 'dash_joinstyle', 'drawstyle')
由于任何Artist 对象具有不同的属性，因此此传输过程的关键是生成属性名称列表以及要传输的正确属性。
有两种方法可以生成属性名称列表：
第一个选项：我们指定要选择的属性。也就是说，我们硬编码一个包含我们想要转移的所有属性的列表。它比第二种选择更艰巨。我们必须为每种类型的对象完全指定属性：这些通常是长列表。仅当我们只处理一种类型的 Artist 对象时，才值得推荐。
第二个选项：我们指定未选择的属性。也就是说，我们用我们不想转移的属性编写一个“例外列表”，我们自动选择对象的所有可转移属性，但在我们的“例外列表”中。这是最快的选择，我们可以同时将它与不同类型的Artist 对象一起使用。
第一个选项：指定传输属性列表
我们只是写了一个赋值来定义我们想要转移的属性列表，如上所示。
此选项的缺点是它不能立即扩展到不同的Artist 对象，例如 Line2D 和 Circle。因为我们必须硬编码不同的属性名称列表，每种类型的 Artist 对象都有一个。
完整示例
我展示了 Line2D Artist 类的示例，如指定的问题中所示。
import matplotlib.pyplot as plt
import numpy as np
# -- Function to attributes copy
#It copies the attributes given in attr_list (a sequence of the attributes names as
# strings) from the object 'obj1' into the object 'obj2'
#It should work for any objects as long as the attributes are accessible by
# 'get_attribute' and 'set_attribute' methods.
def copy_attributes(obj2, obj1, attr_list):
for i_attribute in attr_list:
getattr(obj2, 'set_' + i_attribute)( getattr(obj1, 'get_' + i_attribute)() )
#Creating a figure with to axes
fig = plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212)
plt.tight_layout() #Tweak to improve subplot layout
#create a Line2D object 'line1' via plot
x = np.linspace(0, 2*np.pi, 100)
line1, = ax1.plot(x, np.sin(x))
ax1.set_xlabel('line1 in ax1') #Labelling axis
#Attributes of the old Line2D object that must be copied to the new object
#It's just a strings list, you can add or take away attributes to your wishes
copied_line_attributes = ('xdata', 'ydata', 'animated', 'antialiased', 'color',
'dash_capstyle', 'dash_joinstyle',
'drawstyle', 'fillstyle', 'linestyle', 'linewidth',
'marker', 'markeredgecolor', 'markeredgewidth', 'markerfacecolor',
'markerfacecoloralt', 'markersize', 'markevery', 'pickradius',
'solid_capstyle', 'solid_joinstyle', 'visible', 'zorder')
#Creating an empty Line2D object
line2 = plt.Line2D([],[])
#Copying the list of attributes 'copied_line_attributes' of line1 into line2
copy_attributes(line2, line1, copied_line_attributes)
#Setting the new axes ax2 with the same limits as ax1
ax2.set_xlim(ax1.get_xlim())
ax2.set_ylim(ax1.get_ylim())
#Adding the copied object line2 to the new axes
ax2.add_artist(line2)
ax2.set_xlabel('line2 in ax2') #Labelling axis
plt.show()
输出
第二个选项：指定未传输属性的列表
在这种情况下，我们指定了我们不想转移的属性名称：我们创建一个exception list。我们自动收集Artist 对象的所有可转移 属性，并排除exception list 的名称。
优点是通常对于不同的Artist 对象，排除的属性是相同的短列表，因此，可以更快地编写此选项的脚本。在下面的示例中，列表短至except_attributes = ('transform', 'figure')
本例中的关键函数为list_transferable_attributes，如下图：
#Returns a list of the transferable attributes, that is the attributes having
# both a 'get' and 'set' method. But the methods in 'except_attributes' are not
# included
def list_transferable_attributes(obj, except_attributes):
obj_methods_list = dir(obj)
obj_get_attr = []
obj_set_attr = []
obj_transf_attr =[]
for name in obj_methods_list:
if len(name) > 4:
prefix = name[0:4]
if prefix == 'get_':
obj_get_attr.append(name[4:])
elif prefix == 'set_':
obj_set_attr.append(name[4:])
for attribute in obj_set_attr:
if attribute in obj_get_attr and attribute not in except_attributes:
obj_transf_attr.append(attribute)
return obj_transf_attr
完整示例
import matplotlib.pyplot as plt
import numpy as np
# -- Function to copy, or rather, transfer, attributes
#It copies the attributes given in attr_list (a sequence of the attributes names as
# strings) from the object 'obj1' into the object 'obj2'
#It should work for any objects as long as the attributes are accessible by
# 'get_attribute' and 'set_attribute' methods.
def copy_attributes(obj2, obj1, attr_list):
for i_attribute in attr_list:
getattr(obj2,
'set_' + i_attribute)( getattr(obj1, 'get_' + i_attribute)() )
# #Returns a list of pairs (attribute string, attribute value) of the given
# # attributes list 'attr_list' of the given object 'obj'
# def get_attributes(obj, attr_list):
# attr_val_list = []
# for i_attribute in attr_list:
# i_val = getattr(obj, 'get_' + i_attribute)()
# attr_val_list.append((i_attribute, i_val))
#
# return attr_val_list
#Returns a list of the transferable attributes, that is the attributes having
# both a 'get' and 'set' method. But the methods in 'except_attributes' are not
# included
def list_transferable_attributes(obj, except_attributes):
obj_methods_list = dir(obj)
obj_get_attr = []
obj_set_attr = []
obj_transf_attr =[]
for name in obj_methods_list:
if len(name) > 4:
prefix = name[0:4]
if prefix == 'get_':
obj_get_attr.append(name[4:])
elif prefix == 'set_':
obj_set_attr.append(name[4:])
for attribute in obj_set_attr:
if attribute in obj_get_attr and attribute not in except_attributes:
obj_transf_attr.append(attribute)
return obj_transf_attr
#Creating a figure with to axes
fig = plt.figure()
ax1 = plt.subplot(211) #First axes
ax2 = plt.subplot(212) #Second axes
plt.tight_layout() #Optional: Tweak to improve subplot layout
#create an artist Line2D object 'line1' via plot
x = np.linspace(0, 2*np.pi, 100)
line1, = ax1.plot(x, np.sin(x))
#create an artist Circle object
circle1 = plt.Circle([1,0], 0.5, facecolor='yellow', edgecolor='k')
#Adding the object to the first axes
ax1.add_patch(circle1)
#Labelling first axis
ax1.set_xlabel('line1 and circle1 in ax1')
#Methods that we should not copy from artist to artist
except_attributes = ('transform', 'figure')
#Obtaining the names of line2D attributes that can be transfered
transferred_line_attributes = list_transferable_attributes(line1, except_attributes)
#Obtaining the names of Circle attributes that can be transfered
transferred_circle_attributes = list_transferable_attributes(circle1, except_attributes)
#Creating an empty Line2D object
line2 = plt.Line2D([],[])
circle2 = plt.Circle([],[])
#Copying the list of attributes 'transferred_line_attributes' of line1 into line2
copy_attributes(line2, line1, transferred_line_attributes)
copy_attributes(circle2, circle1, transferred_circle_attributes)
#attr_val_list_line2 = get_attributes(line2, line1_attr_list)
#Setting the new axes ax2 with the same limits as ax1
ax2.set_xlim(ax1.get_xlim())
ax2.set_ylim(ax1.get_ylim())
#Adding the copied object line2 to the new axes
ax2.add_line(line2) #.add_artist(line2) also possible
ax2.add_patch(circle2) #.add_artist(circle2) also possible
ax2.set_xlabel('line2 and circle2 in ax2') #Labelling axis
plt.show()
输出