Splitting string into different line lengths

Question

I'm trying to split a variable length string across different but predefined line lengths. I've thrown together some code below which fails on key error 6 when I plonk it into Python Tutor (I don't have access to a proper python IDE right now) I guess this means my while loop isn't working properly and it's trying to keep incrementing lineNum but I'm not too sure why. Is there a better way to do this? Or is this easily fixable?

The code:

import re

#Dictionary containing the line number as key and the max line length
lineLengths = {
        1:9,
        2:11,
        3:12,
        4:14,
        5:14
               }

inputStr = "THIS IS A LONG DESC 7X7 NEEDS SPLITTING"        #Test string, should be split on the spaces and around the "X"

splitted = re.split("(?:\s|((?<=\d)X(?=\d)))",inputStr)     #splits inputStr on white space and where X is surrounded by numbers eg. dimensions

lineNum = 1                         #initialises the line number at 1

lineStr1 = ""                           #initialises each line as a string
lineStr2 = ""
lineStr3 = ""
lineStr4 = ""
lineStr5 = ""

#Dictionary creating dynamic line variables
lineNumDict = {
        1:lineStr1,
        2:lineStr2,
        3:lineStr3,
        4:lineStr4,
        5:lineStr5
        }

if len(inputStr) > 40:
    print "The short description is longer than 40 characters"
else:
    while lineNum <= 5:
        for word in splitted:
            if word != None:
                if len(lineNumDict[lineNum]+word) <= lineLengths[lineNum]:
                    lineNumDict[lineNum] += word
                else:
                    lineNum += 1
            else:
                if len(lineNumDict[lineNum])+1 <= lineLengths[lineNum]:
                    lineNumDict[lineNum] += " "
                else:
                    lineNum += 1

lineOut1 = lineStr1.strip()
lineOut2 = lineStr2.strip()
lineOut3 = lineStr3.strip()
lineOut4 = lineStr4.strip()
lineOut5 = lineStr5.strip()

I've taken a look at this answer but don't have any real understanding of C#: Split large text string into variable length strings without breaking words and keeping linebreaks and spaces

Answer 1

It doesn't work because you have the for words in splitted loop inside your loop with the lineLen condition. You have to do this:

    if len(inputStr) > 40:
        print "The short description is longer than 40 characters"
    else:
        for word in splitted:
            if lineNum > 5:
                 break
            if word != None:
                if len(lineNumDict[lineNum]+word) <= lineLengths[lineNum]:
                    lineNumDict[lineNum] += word
                else:
                    lineNum += 1
            else:
                if len(lineNumDict[lineNum])+1 <= lineLengths[lineNum]:
                    lineNumDict[lineNum] += " "
                else:
                    lineNum += 1

Also lineStr1, lineStr2 and so on won't be changed, you have to access the dict directly (strings are immutable). I tried it and got the results working:

    print("Lines: %s" % lineNumDict) 

Gives:

    Lines: {1: 'THIS IS A', 2: 'LONG DESC 7', 3: '7 NEEDS ', 4: '', 5: ''}

Answer 2

for word in splitted:
    ...
    lineNum += 1

your code increments lineNum by the number of words in splitted, i.e. 16 times.

Answer 3

I wonder if a properly commented regular expression wouldn't be easier to understand?

lineLengths = {1:9,2:11,3:12,4:14,5:14}
inputStr = "THIS IS A LONG DESC 7X7 NEEDS SPLITTING" 
import re
pat = """
(?:                     # non-capture around the line as we want to drop leading spaces
    \s*                 # drop leading spaces
    (.{{1,{max_len}}})  # up to max_len characters, will be added through 'format'
    (?=[\b\sX]|$)       # and using word breaks, X and string ending as terminators
                        # but without capturing as we need X to go into the next match
)?                      # and ignoring missing matches if not all lines are necessary
"""

# build a pattern matching up to 5 lines with the corresponding max lengths
pattern = ''.join(pat.format(max_len=x) for x in lineLengths.values())

re.match(pattern, inputStr, re.VERBOSE).groups()
#  Out: ('THIS IS A', 'LONG DESC 7', '7 NEEDS', 'SPLITTING', None)

Also, there is no real point in using a dict for line_lengths, a list would do nicely.