Unicode string in Matplotlib annotate

Question

I have the following code, when ever label has a unicode string, annotate fails throwing error, how do i resolve this?

from matplotlib import pyplot as plt
import numpy as Math


X = Math.genfromtxt(inputFile,autostrip=True,comments=None,dtype=Math.float64,usecols=(range(1,dim+1)))
labels = Math.genfromtxt(inputFile,autostrip=True,comments=None,dtype='str',usecols=(0))
Y = some_function(X, 2, 50, 20.0);    
fig = plt.figure()
ax = fig.add_subplot(111)
plt.scatter(Y[:,0],Y[:,1])
for l,x,y in zip(labels,Y[:,0],Y[:,1]):
   ax.annotate('(%s)' %l, xy=(x,y), textcoords='offset points')

plt.grid()
plt.show()

Error :
Traceback (most recent call last):
ax.annotate('(%s)' %unicode(l), xy=(x,y), textcoords='offset points')
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 4: ordinal not in range(128)

Community · Accepted Answer · 2017-05-23 12:08:40Z

2

You need to decode the string as unicode rather than standard ASCII (see here):

from matplotlib import pyplot as plt

l = '\xe2'

plt.annotate('%s' % l, (0, 0))
# raises UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 0: ordinal not in range(128)

plt.annotate('%s' % l.decode('unicode-escape'), (0, 0))
# works

You could also decode your input file as unicode like this:

# converter function that decodes a string as unicode
conv = {0:(lambda s: s.decode('unicode-escape'))}

labels = np.genfromtxt(inputFile, dtype='unicode', converters=conv, usecols=0)

labels.dtype will then be unicode ('<Ux') instead of string ('|Sx') and therefore ax.annotate('(%s)' %l, ...) will work.

edited May 23, 2017 at 12:08

CommunityBot

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answered Feb 11, 2015 at 15:52

ali_m

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3 Comments

Lanc Over a year ago

Thanks! First option works for me, but the second doesn't work

ali_m Over a year ago

When you say it "doesn't work", could you be more specific? Does the error occur in genfromtxt or in annotate? It would be helpful if you could show what your inputFile looks like in your question.

ali_m Over a year ago

I figured out the problem - it's necessary to pass a converter argument to genfromtxt which decodes the input string as unicode. I've updated my answer to include this.

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