How do I create a non-ascii dendrogram with Python?

Trying to create a dendrogram with this found code block, and it works up until the call:

r('mt_dist <- dist(t(mt))')

then spouts the error:

RPy_RException: Error in dist(t(mt)) : (list) object cannot be coerced to type 'double'

up until that point it was looking good ... I'm probably missing something really simple

Any help?

#importing modules
from numpy import array
from random import normalvariate,shuffle
from rpy import r

# creating a random matrix
# creating it with different 'samples' in different columns
mt = []
for l in range(20): #20 lines
    line = []
    means = range(1,9)
    for c in range(8): # 8 columns
        #Colum 1: mean 1; Column 2: mean 2.... values normally distributed s.d. = 0.5       
        line.append(normalvariate(means.pop(), 0.5))

    mt.append(line)

# once we have a matrix, transform it in an array
mt_array = array(mt)

# The R work
# Pass the array to 'mt' variable in R
r.assign("mt", mt_array)

# manipulate R via r('command')
r('print(mt)') #print the matrix 'mt' to check values

#The clusteri开发者_JAVA百科ng process
#Calculating distances with 'dist'
#'dist' calculates distance among lines, so I am transposing (with t()) in order to have my columns clustered
## I guess 'dist' uses euclidian distance as default

r('mt_dist <- dist(t(mt))')
# hclust does the clustering with upgma as default

r('result = hclust(mt_dist)')

# directs the output to a determinde file
r('png("output_file.png")')

# plot the result
labels = ["sample A", "sample B","sample C", "sample D","sample E", "sample F", "sample G", "sample H"]
r.assign("labels", labels)
r('plot(result, labels=labels, main="My title")')

# 'close' you output
r('dev.off()')

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This is not answer to your RPy_... exception problem. Rather providing answer to your title How do I create a non-ascii dendrogram with Python?. You may try this to plot dendrogram.