A 'too many values to unpack' error in python

Question

import pylab as pl

data = """AP 10
AA 20
AB 30
BB 40
BC 40
CC 30
CD 20
DD 10"""

grades = []
number = []

for line in data.split("/n"):
     x, y = line.split()
     grades.append(x)
     number.append(int(y))       
fig = pl.figure()
ax=fig.add_subplot(1,1,1)
ax.bar(grades,number)
p.show()

This is my code, i wish to make a bar graph, from the data. Initially when I run my code, I was getting an indentation error, in line 17, after adding a space to all the entire for block, I started getting this 'too many values to unpack error', in line 16. I am new to python, and I don't know how to proceed now.

Answer 1

The problem is that your for-loop is splitting at the wrong token (/n) instead of \n.

But when you only want to split the newlines there actually is a splitlines()-method on strings that does just that: you should actually use this method, because it will handle different newline delimiters between *nix and Windows as well (*nix systems typically denote newlines via \r\n, whereas Windows uses \n and the old Mac OS uses \r: check the Python documentation for more information)

Your error occurs on the next line: due to the fact that the string was not split into lines your whole string will now be split on the whitespace, which will produces many more values than the 2 you try to assign to a tuple.

Answer 2

You have a line that does not have two items on it:

 x, y = line.split()

did not split to two elements and that throws the error. Most likely because you are not splitting your data variable properly and have the whole text as one long text. /n does not occur in your data data.

Use .splitlines() instead:

for line in data.splitlines():
     x, y = line.split()