Arithmetic arranger - issue with characters added to return

Hello,

I’m currently on the arithmetic arranger problem described here https://repl.it/github/freeCodeCamp/boilerplate-arithmetic-formatter

My code seems very close to the expected result, BUT on some iterations there is a random

“F”

or a random

“.”

that is printed right before

This is arranged_problems

(which I use to visualize what my function returns).
It’s visible on loops 3 to 7. I don’t seem to have any capital F in my code, and I’ve also double-checked all the “.” and can’t understand where they come from.

Many thanks ahead for your help!

My code:

def arithmetic_arranger(problems, calc = False):
  #initialize all values that are needed outside of the loop
  pbl_firstsplit = []
  pbl_secondsplit = []
  pbl_secondsplit_padded = []
  pbl_line1 = []
  pbl_line2 = []
  pbl_line3 = []
  pbl_line4 = []
  pbl_line1_joined = []
  pbl_line2_joined = []
  pbl_line3_joined = []
  pbl_line4_joined = []
  return_iffalse = []
  return_iftrue = []
  arranged_problems = []
  
  # 1. count number of problems
  count_problems_elements = len(problems)
  
  # 2. identified non-authorised operators
  substring_multiply = "*"
  substring_divide = "/"
  count_wrongoperators = str(problems).count(substring_divide) + str(problems).count(substring_multiply) 

# 3. regex to check on nb of digits
  import re
  regex_maxfourdigits = '\d{5,}'
  str_problems = str(problems)
  match_maxfourdigits = re.search(regex_maxfourdigits, str_problems)
  match_findnondigits = re.search('[a-zA-Z]', str_problems)
  
# make problems_str a string so it can be split
  problems_str = str(problems)

  #loop on the list of problems
  i = 0
  while i < len(problems): 
    pbl = problems[i]
    
    # split each element within each problem - will be used to compute a result later on
    pbl_split1 = pbl.split()
    pbl_firstsplit.append(pbl_split1)
    calc1 = pbl_firstsplit[i][0]
    operator = pbl_firstsplit[i][1]
    calc2 = pbl_firstsplit[i][2]
    
    #now I have to re-split the pbl string to have "element one", "operator space element 2"
    pbl_split2 = pbl.split(" ",1)
    pbl_secondsplit.append(pbl_split2)

    # now I will pad the elements using rjust 
    pbl_split2_str = str(pbl_split2)
    longest_inpbl = max(pbl_split2, key=len)
    len_longest_inpbl = len(longest_inpbl)
    padded = [str(i).rjust(len_longest_inpbl, ' ') for i in pbl_split2] 
    pbl_secondsplit_padded.append(padded)
    
    #now appending the formatted elements to each list
    pbl_line1.append(pbl_secondsplit_padded[i][0] + " " * 4)
    pbl_line1_joined = ''.join(pbl_line1)
    pbl_line2.append(pbl_secondsplit_padded[i][1] + " " * 4)
    pbl_line2_joined = ''.join(pbl_line2)
    pbl_line3.append("-"* len(pbl_secondsplit_padded[i][0]) + " " * 4)
    pbl_line3_joined = ''.join(pbl_line3)

    # doing the computation only if a True argument is passed
    if calc == True: 
      if operator == '+': 
        result = int(calc1) + int(calc2)
      else: 
        result = int(calc1) - int(calc2)
      result_padded = str(result).rjust(len_longest_inpbl, ' ')
      pbl_line4.append(result_padded)
      pbl_line4.append(" " * 4)
      pbl_line4_joined = ''.join([str(i) for i in pbl_line4])
      return_iftrue = "\n" +str(pbl_line1_joined) + "\n" + str(pbl_line2_joined) + "\n" + str(pbl_line3_joined) + "\n" + str(pbl_line4_joined)

    else: 
      return_iffalse = "\n" + str(pbl_line1_joined) + "\n" + str(pbl_line2_joined) + "\n" + str(pbl_line3_joined)
    i+=1
  
  # error in nb of problems
  if int(count_problems_elements) > 4: 
    arranged_problems ="Error: Too many problems."

# error in operators, ie if string contains * or / 
  elif count_wrongoperators > 0: 
    arranged_problems ="Error: Operator must be '+' or '-'."

# error if any number is more than 4 digit long
  elif match_maxfourdigits is not None: 
    arranged_problems = "Error: Numbers cannot be more than four digits."

  elif match_findnondigits is not None:
    arranged_problems = "Error: Numbers must only contain digits."

# if all else ok, convert
  elif calc == True:
    arranged_problems = return_iftrue
    
  else:
    arranged_problems = return_iffalse

  print("***This is arranged_problems: *** "+arranged_problems)

  return arranged_problems

This is my output:

***This is arranged_problems: *** 
   32    3801      45     123    
+ 698     - 2    + 43    + 49    
-----    ----    ----    ----    

   32    3801      45     123    
+ 698     - 2    + 43    + 49    
-----    ----    ----    ----    
***This is arranged_problems: *** 
    3    3801      45     123    
+ 855     - 2    + 43    + 49    
-----    ----    ----    ----    
F***This is arranged_problems: *** Error: Operator must be '+' or '-'.
.***This is arranged_problems: *** Error: Numbers must only contain digits.
.***This is arranged_problems: *** 
   32         1      45     123    
- 698    - 3801    + 43    + 49    
-----    ------    ----    ----    
 -666     -3800      88     172    
F***This is arranged_problems: *** Error: Numbers cannot be more than four digits.
.***This is arranged_problems: *** Error: Too many problems.
.