TypeError: 'NoneType' object is not iterable - Python

Question

I know this question has been asked before but I can't seem to get mine working. Can someone help me out with this?

import sys

class Template:
    def processVariable(self, template, data):
        first = template.find('{{')
        second = template.find('}}')
        second = second + 2
        out = template[first+second]
        assert[out.startswith('{{')]
        out = out.strip('{}')
        rest = template[second:]
        if out in data:
            newstring = data[out]
            return(rest, newstring)
        else:
            print "Invalid Data Passed it"

t = Template()
vars = {
    'name': 'Jane',
    'course': 'CS 1410',
    'adjective': 'shimmering'
}

(rest, out) = t.processVariable('{{name}} is in {{course}}', vars)

This is the error I am getting:

File "template.py", line 28, in <module>
    (rest, out) = t.processVariable('{{name}} is in {{course}}', vars)
TypeError: 'NoneType' object is not iterable

I understand the NoneType but is it because of my for loop or did I just miss something simple? Thanks in advance!

My code will be passed into a field so that my teacher can run a code against it and it will pass or fail. This is what his code will run:

import Candidate

t = Candidate.Template()
vars = {
    'name': 'Jane',
    'course': 'CS 1410',
    'adjective': 'shimmering'
}

(rest, out) = t.processVariable('{{course}} is {{adjective}}', vars)
print 'rest is: [' + rest + ']'
print 'out is : [' + out + ']

what it should return is:

rest is: [ is in {{course}}]
out is : [Jane]

it will return Yes or No if it worked.

Solution 1

There are errors in your code.

This:

out = template[first+second]
assert[out.startswith('{{')]

Should be:

out = template[first:second]
assert out.startswith('{{')

And:

    else:
        print "Invalid Data Passed it"

Should probably be:

    else:
        raise ValueError('Invalid data')

Also this functionality is already in Python:

from string import Template
t = Template('$name is in $course')

vars = {
    'name': 'Jane',
    'course': 'CS 1410',
    'adjective': 'shimmering'
}

print(t.substitute(vars))

Output:

Jane is in CS 1410

Solution 2

You didn't return anything from your else part, and hence your function will by default return None.

Ad of course, you cannot unpack a None into two variables. Try returning a tuple from your else part like this:

if out in data:
    newstring = data[out]
    return (rest, newstring)
else:
    print "Invalid Data Passed it"
    return (None, None)

Comments

[Rohit Jain]

I don't see any for loop in there. Have you posted the complete code?

[Nick McArthur]

I meant the if statement...sorry

[Nick McArthur]

Gotcha! So I made the change now I am getting this error: Invalid Data Passed it

[Rohit Jain]

Where are you using the returned tuple? Also, what exactly are you trying to do?

[Rohit Jain]

@NickMcArthur. Ok, it seems all right. You are only getting that message you printed in the else part. And your function returns the (None, None) tuple. Try to print the value of variables rest and out, after the function call.

[Nick McArthur]

Thank you sooooo much! That was it!

[Nick McArthur]

Thank you for your help with this! I appreciate it!