复制matplotlib艺术家

时间:2016-10-11 11:09:21

标签: python python-3.x matplotlib copy

我使用matplotlib创建了一个Line2D对象数组,我想在各种图中使用它。但是,在我看到的情况下,在多个地块中使用相同的艺术家并不起作用:

RuntimeError: Can not put single artist in more than one figure

正如我发现的那样,艺术家曾经附着在一个轴上,不能再附着在另一个轴上了。 好吧,我的想法是简单地复制包含带有copy()的行的数组,但它不会起作用。复制的数组仍然引用相同的对象。我想,那是因为你根本无法复制艺术家(?)。

有没有办法避免重新计算Line2D并且只需计算一次?

1 个答案:

答案 0 :(得分:1)

我非常希望copy的{​​{3}}中有一个matplotlibs方法!

也许有人想将下面的代码改编到Artist Class中,以便采用一种transfer方法将一个Artist对象复制到另一个对象中。

走错路

对包copy中的对象使用标准的deepcopycopy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,然后通过循环将所有必要的属性从原始对象转移到新创建的对象中。 / p>

我定义的此函数是将属性值从一个对象传输到另一个对象的工具:

# -- 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)() )

在此功能中,最重要的参数是attr_list。这是我们要从obj1复制到obj2的属性名称的列表,例如,对于对象Artist.Line2D,它可能是attr_list = ('xdata', 'ydata', 'animated', 'antialiased', 'color', 'dash_capstyle', 'dash_joinstyle', 'drawstyle')

由于任何Artist对象都具有不同的属性,因此此传输过程的关键是生成具有正确属性的属性名称列表

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,我们硬编码包含要传输的所有属性的列表。它比第二种选择更为艰巨。我们必须为每种类型的对象完全指定属性:这些通常是很长的列表。仅当我们只处理一种类型的Artist对象时,才建议这样做。

  • 第二个选项:我们指定选择的属性。也就是说,我们编写了一个“例外列表”,其中包含我们不想转移的属性,我们会自动选择对象的所有可转移属性,但会选择“例外列表”中的那些属性。这是最快的选项,我们可以同时将其与不同类型的Artist对象一起使用。

第一个选项:指定已传输属性的列表

我们只是编写了一个赋值以定义我们要转移的属性列表,如上所示。

此选项的缺点是无法立即扩展到不同的Artist对象,例如Line2D和Circle。因为我们必须对不同的属性名称列表进行硬编码,所以每种Artist对象的类型都是一个。

完整示例

按照指定的问题,我将显示Line2D Artist类的示例。

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:我们制作了exception list。我们会自动收集Artist对象的所有 transferable 属性,并排除我们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,此选项可以更快速地编写脚本。在下面的示例中,列表最短为except_attributes = ('transform', 'figure')

在这种情况下,关键功能是list_transferable_attributes,如下所示:

#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