使用pylab.scatter和CMAP在Python 3.5.1

Question

當我使用Python2，我可以繪製圖表

from sklearn import datasets 
from matplotlib.colors import ListedColormap 
circles = datasets.make_circles() 

colors = ListedColormap(['red', 'blue']) 
pyplot.figure(figsize(8, 8)) 

pyplot.scatter(map(lambda x: x[0], circles[0]), map(lambda x: x[1], circles[0]), c = circles[1], cmap = colors) 

但是當我使用Python3，我不能這樣做。我試圖改變顏色，但不能。

我收到許多錯誤：

ValueError: length of rgba sequence should be either 3 or 4 

During handling of the above exception, another exception occurred: 

ValueError: to_rgba: Invalid rgba arg "[0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 1 0 0 1 1 1 0 1 0 0 1 1 0 1 0 0 0 0 1 0 0 1 0 1 1 1 0 1 0 1 0 1 0 1 1 1 1 1 1 0 0 1 0 1 1 1 1 1 1 1 0 0 0 1 1 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 0 1 1 0 1 0 1 0 1 1 0 0 0 0 1]" 
length of rgba sequence should be either 3 or 4 

During handling of the above exception, another exception occurred: 

ValueError: Color array must be two-dimensional 

我該如何解決這個問題？

Answer 1

問題是map does not return a list in Python 3。您可以通過map到list或使用列表理解，這實際上是比你的拉姆達短：

pyplot.scatter([x[0] for x in circles[0]], 
       [x[1] for x in circles[0]], c=circles[1], cmap=colors) 

更短的版本擺脫了地圖完全的：

pyplot.scatter(*zip(*circles[0]), c=circles[1], cmap=colors)