Python split function. Too many values to unpack error

I have a python function that must read data from file and split it into two key and value, and then store it in dictionary. Example: file:

http://google.com 2
http://python.org 3
# and so on a lot of data

I use the split function for it, but when there is really a lot of data it raises value error

ValueError: too many values to unpack

What can I do about this ?

This is the exact code that fails

with open(urls_file_path, "r") as f:
    for line in f.readlines():
        url, count = line.split()# fails here
        url_dict[url] = int(count)

You are trying to unwrap the split list in to these two variables.

url, count = line.split()

What if there is no space or two or more spaces? Where will the rest of the words go?

data = "abcd"
print data.split()    # ['abcd']
data = "ab cd"
print data.split()    # ['ab', 'cd']
data = "a b c d"
print data.split()    # ['a', 'b', 'c', 'd']

You can actually check the length before assigning

with open(urls_file_path, "r") as f:
    for idx, line in enumerate(f, 1):
        split_list = line.split()
        if len(split_list) != 2:
            raise ValueError("Line {}: '{}' has {} spaces, expected 1"
                .format(idx, line.rstrip(), len(split_list) - 1))
        else:
            url, count = split_list
            print url, count

With the input file,

http://google.com 2
http://python.org 3
http://python.org 4 Welcome
http://python.org 5

This program produces,

$ python Test.py
Read Data: http://google.com 2
Read Data: http://python.org 3
Traceback (most recent call last):
  File "Test.py", line 6, in <module>
    .format(idx, line.rstrip(), len(split_list) - 1))
ValueError: Line 3: 'http://python.org 4 Welcome' has 2 spaces, expected 1

Following @abarnert's comment, you can use partition function like this

url, _, count = data.partition(" ")

If there are more than one spaces/no space, then count will hold rest of the string or empty string, respectively.

If you are using Python 3.x, you can do something like this

first, second, *rest = data.split()

First two values will be assigned in first and second respectively and the rest of the list will be assigned to rest, in Python 3.x

Python split function. Too many values to unpack error

Related

Recent Posts