[Tutor] Dictionary and List Question?
pythontutor at venix.com
Thu Nov 13 09:39:21 EST 2003
Clay Shirky wrote:
> if entry in list:
> list[entry] += 1
> list[entry] = 1
I think your naming could be improved. list is used by python for
the list type. Using list as a variable name prevents you from
calling the list type. In addition, list is really a dictionary.
I'll use d_lines instead of list for my code snippet.
d_lines[entry] = d_lines.setdefault(entry, 0) + 1
setdefault will create the dictionary entry with an initial value,
zero in this case. Then we always add one to count each line reference.
Python Quick Reference
This is a real handy reference for looking up functions and methods. (I've
downloaded the relevant version for me to minimize the load on their server.)
> Next, I want to loop through the dictionary list, and take each key-value
> pair, and turn them into a string of value-key, so that the number is first,
> and then the line. Then I want to sort them so that the lines appear in
> numerical order.
You can sort a list of tuples as well as strings.
l_lines = [(v,k) for (k,v) in d_lines.items()]
l_lines.sort() # v is still a number so it will sort correctly
Now you can turn the sorted list of counts and lines into strings for output.
1 Court Street, Suite 378
Lebanon, NH 03766-1358
More information about the Tutor