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Implemented __copy__ in Colormap #8314

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Implemented __copy__ in Colormap #8314

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3ed55f4
Added __copy__ to Colormap
vidursatija Mar 17, 2017
5003047
Updated __copy__ in Colormap
vidursatija Mar 17, 2017
82cccd0
Fixed __copy__ indentation
vidursatija Mar 17, 2017
3ece4cb
Updated __copy__ indentation
vidursatija Mar 17, 2017
7e8a940
Added tests for Colormap copy
vidursatija Mar 19, 2017
5cafb57
Update test_colors.py
vidursatija Mar 19, 2017
3e6a689
Fixed copy test function
vidursatija Mar 19, 2017
f7eadbf
Fixed indentation
vidursatija Mar 19, 2017
eeae70d
Changed copy test
vidursatija Mar 24, 2017
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Fixed __copy__ indentation
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@vidursatija
vidursatija authored Mar 17, 2017
commit 82cccd003e1a9eff6fcca7de9f24fcd44a2b4657
17 changes: 8 additions & 9 deletions lib/matplotlib/colors.py
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Original file line number Diff line number Diff line change
Expand Up @@ -532,15 +532,14 @@ def __call__(self, X, alpha=None, bytes=False):

def __copy__(self):
"""Create new object with the same class and update attributes
If object is initialized, copy the elements of _lut list
"""
cls = self.__class__
newCMapObj = cls.__new__(cls)
newCMapObj.__dict__.update(self.__dict__)
if self._isinit:
newCMapObj._lut = np.copy(self._lut)
return newCMapObj

If object is initialized, copy the elements of _lut list
"""
cls = self.__class__
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Is this really the best way to do this? It seems to be dropping down to a low layer of python.

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The low layer of python is presumably faster than the normal python code. Another way of doing this would be creating a normal Colormap object and manually copying each attribute.

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How should I implement a test?

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Get a color map, use it (cm([-1, 0, .5, 1, np.nan, np.inf]), copy it, use set_bad, set_over, set_under on one or both of them, use them both and check that the colors come back as expected.

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I would not expect this to be much faster. If you think it is can you bench mark it?

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I will bench mark it and implement the tests. I'll post the results soon.

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I have bench marked the 2 functions.
The following code is used:

import matplotlib.pyplot as plt
import time

cm = plt.cm.Reds

start = time.time()
cm2 = cm.copy_1()     #Using low level python
end1 = time.time()
cm3 = cm.copy_2()     #Copying the attributes manually
end2 = time.time()
print("Method 1 :" + str(end1-start))
print("Method 2 :" + str(end2-end1))

I get the following output:
Method 1 :1.8358230590820312e-05
Method 2 :2.6941299438476562e-05

I can definitely say that using low level python functions would lead to a simpler, faster code, which might be a little difficult to understand by seeing it.

Test

I've used the copy_1 function to copy the object.

import numpy as np
import matplotlib.pyplot as plt

cm = plt.cm.Reds
cm([-1, 0, .5, np.nan, np.inf])

cm.set_bad('y')
cm2 = cm.copy_1()
cm2.set_bad('b')
print(cm._rgba_bad)
print(cm2._rgba_bad)

cm.set_under('y')
cm2.set_under('r')
print(cm._rgba_under)
print(cm2._rgba_under)

cm.set_over('c')
cm2.set_over('m')
print(cm._rgba_over)
print(cm2._rgba_over)

Output is as follows:
(0.75, 0.75, 0.0, 1)
(0.0, 0.0, 1.0, 1)
(0.75, 0.75, 0.0, 1)
(1.0, 0.0, 0.0, 1)
(0.0, 0.75, 0.75, 1)
(0.75, 0.0, 0.75, 1)

As we can see, using the function on both Colormaps doesn't change the other

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My last commit (3ece4cb) has used lower level python to implement copy. The code has also used spaces instead of tabs

newCMapObj = cls.__new__(cls)
newCMapObj.__dict__.update(self.__dict__)
if self._isinit:
newCMapObj._lut = np.copy(self._lut)
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Please use spaces instead of tabs

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I'll update it

return newCMapObj

def set_bad(self, color='k', alpha=None):
"""Set color to be used for masked values.
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