CODEWITHSUNDEEP
pythonpython-3.x
newbie12345
newbie12345

Reputation: 1

Why does x count as a list, even though its definition as a list only comes later in the code?

So I've been reading through "Python for Everybody" and was trying to complete chapter 11 exercise 2 when my code didn't work.

fhand = open("mboxshort.txt")
summation = list()
count = 0
import re
for line in fhand:
    line = line.rstrip()
    x = re.findall("^New Revision:\s([0-9]+)", line)
    if len(x) > 0:
        x = float(x)
        summation.append(x)
        count += 1
print(sum(summation)/count)

The error that comes up is: TypeError: float() argument must be a string or a real number, not 'list'. My question is why does it count x as a list when it's a string to begin with, and how do I fix this error?

Upvotes: 0

Views: 32

Answers (1)

Leonardo Lima
Leonardo Lima

Reputation: 413

Check re.findall() documentation, you will see that it returns a list!

Taking a look into its source code:

def findall(pattern, string, flags=0):
    """Return a list of all non-overlapping matches in the string.

    If one or more capturing groups are present in the pattern, return
    a list of groups; this will be a list of tuples if the pattern
    has more than one group.

    Empty matches are included in the result."""
    return _compile(pattern, flags).findall(string)

That's why you can't cast x to float!

In doubt, you can check its type:

print(type(x))

<class 'list'>

Upvotes: 1

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