FAQ: Code Challenge: String Methods - Substring Between


This community-built FAQ covers the “Substring Between” exercise from the lesson “Code Challenge: String Methods”.

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FAQs on the exercise Substring Between

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def substring_between_letters(word, start, end):
mystring = [word.find(start)-1:word.find(end)]:
return mystring
I think this should work but im getting a syntax error.


This worked just fine for me:

Write your substring_between_letters function here:

def substring_between_letters(word, start, end):
s = word.find(start) + 1
e = word.find(end)
if s < 0 or e < 0:
return word
return word[s:e]

Uncomment these function calls to test your tip function:

print(substring_between_letters(“apple”, “p”, “e”))

should print “pl”

print(substring_between_letters(“apple”, “p”, “c”))

should print “apple”


Curious why my code didn’t work. I must be missing something in the fun. Could not solve for ‘pl’

def substring_between_letters(word, start, end):
  if word.find(start) < 0 or word.find(end) < 0:
    return word

Why not just use:

You also forgot the return in your else.


def substring_between_letters(word,start,end):
the_list =
the_end_list =
for i in range(0,len(word)):
if(word [i] == start):
for j in range(len(word)-1,-1,-1):
if(word [j] == end):
return word[the_list[0]:the_list[-1]]
I get a warning that int object is not subscriptable. I am wondering Why cannot I acces my list in the function


How should our function handle other cases, like where the “start” character appears after the “end character”?

For example, should this code:

substring_between_letters(word = "adogb", start  = "b", end = "a")

return “dog”, or simply return the word “adogb”

Another case is if the two arguments appear in the proper order, but only after they appear in the wrong order, like

substring_between_letters(word = "adogbruna", start = "b", end = "a"

Should this print “dog”, “run”, or the word?


Substring Between

print (substring_between_letters("adogbruna", "b", "a"))
# adogbruna
print (substring_between_letters("dogbruna", "b", "a"))
# run

The first example returns the full word because a comes before b, and we cannot have the end at the beginning.

The second example we remove the starting a, and get the result we expect since a is at the end, and b does precede it.

Similarly, your first example should also return the full word. Switch the a and b around and it will return dog.

1 Like
#with .find() method (super sloppy. System's answer was much better formatted)
def substring_between_letters(word, start, end):
  answer = word[word.find(start) + 1 : word.find(end)]
  if word.find(end) == -1:
    return word
  elif word.find(start) == -1:
    return word
    return answer
#Without .find() method
# Write your substring_between_letters function here:

def substring_between_letters(word, start, end):
  start_value = 0
  end_value = 0
  while start_value < len(word):
    if word[start_value] != start:
      start_value += 1
  while end_value > -len(word):
    if word[end_value] != end:
      end_value += -1
  if start_value == len(word):
    return word
  elif end_value == -len(word):
    return word
    return word[start_value + 1: end_value]
# Uncomment these function calls to test your function:
print(substring_between_letters("apple", "p", "e"))
# should print "pl"
print(substring_between_letters("apple", "p", "c"))
# should print "apple"```