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)
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Answer
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