list to string using "".join() - issues with passing a list of lists of strings

I feel like maybe this is an issue with using "".join() with a list of lists of strings instead of a list of strings, but haven't found an answer.

Maybe it's something else that I am missing.

I hope my notes show what I have been trying (to take a list of strings turn them into a str and append 'scramble' with that string)

# SCRAMBLE WORD/PHRASE
# IMPORTS
import random

# VARIABLES
test_words_list = ["dark", "happy holidays", "computer", "I like pie", "dogs love pizza"]

# FUNCTIONS
#function too big? cut down into smaller? or too small to be worth it?

def scramble_string(string, seperate_words = False):
  scramble = ""
  if seperate_words == False:
    """Remove spaces & scramble all letters together into one string"""
    words_list = string.split(" ")          # removes whitespace (list)
    print(f"letters_list= {words_list}")
    for word_str in words_list:
      word_letter_list = [letter for letter in word_str]
      print(f"word_letters_list = {word_letter_list}")
      random.shuffle(word_letter_list)
      print(f"After shuffle word_letters_list = {word_letter_list}")
      word_letter_str = "".join(word_letter_list)
      print(f"word_letter_str = {word_letter_str}")
      scramble += word_letter_str
      print(f"scramble = {scramble}")
    return scramble
  else:
    """scramble letters in words without mixing letters from different words.
    List words in same order with space between, but with letters scrambled"""
    scrambled_list = []
    words_list = string.split()                      # passed string into list of strings
    print(f"words_list = {words_list}")
    for word_str in words_list:
      letters_list = [letter for letter in word_str]
      print(f"letters_list = {letters_list}")
      random.shuffle(letters_list)
      print(f"After shuffle letters_list = {letters_list}")
      scrambled_list.append(letters_list)            # list of lists
      print(f"scrambled_list = {scrambled_list}")

      # vv PROBLEM vv
      scrambled_str = "".join(scrambled_list)  #"sequence item 0: expected str instance, list found"
      scramble += scrambled_str
      #scramble = ''.join(str(scrambled_list)[1:-1]) # makes scramble a list???
      print(f"scramble = {scramble}")
  return scramble

# Tests

#print(scramble_string(test_words_list[1]))          # WORKS (returned = "hyppahadsilyo")
print(scramble_string(test_words_list[-1], True))    # returns =

Update your list of list of string to list of string first. I did that at this line.

scrambled_list.append("".join(letters_list))            # list of lists

Instead of appending list of strings to a list, I am combining that list of letters to form a word and appending that scrambled word to the scrambled_list.

import random
# VARIABLES
test_words_list = ["dark", "happy holidays", "computer", "I like pie", "dogs love pizza"]
# FUNCTIONS
#function too big? cut down into smaller? or too small to be worth it?
def scramble_string(string, seperate_words = False):
scramble = ""
if seperate_words == False:
"""Remove spaces & scramble all letters together into one string"""
words_list = string.split(" ")		  # removes whitespace (list)
print(f"letters_list= {words_list}")
for word_str in words_list:
word_letter_list = [letter for letter in word_str]
print(f"word_letters_list = {word_letter_list}")
random.shuffle(word_letter_list)
print(f"After shuffle word_letters_list = {word_letter_list}")
word_letter_str = "".join(word_letter_list)
print(f"word_letter_str = {word_letter_str}")
scramble += word_letter_str
print(f"scramble = {scramble}")
return scramble
else:
"""scramble letters in words without mixing letters from different words.
List words in same order with space between, but with letters scrambled"""
scrambled_list = []
words_list = string.split()					  # passed string into list of strings
print(f"words_list = {words_list}")
for word_str in words_list:
letters_list = [letter for letter in word_str]
print(f"letters_list = {letters_list}")
random.shuffle(letters_list)
print(f"After shuffle letters_list = {letters_list}")
scrambled_list.append("".join(letters_list))			# list of lists
print(f"scrambled_list = {scrambled_list}")
# vv PROBLEM vv
scrambled_str = "".join(scrambled_list)  #"sequence item 0: expected str instance, list found"
scramble += scrambled_str
#scramble = ''.join(str(scrambled_list)[1:-1]) # makes scramble a list???
print(f"scramble = {scramble}")
return scramble
# Tests
# print(scramble_string(test_words_list[1]))		  # WORKS (returned = "hyppahadsilyo")
print(scramble_string(test_words_list[-1], True))

This is the function now working correctly (with basic improvements) for anyone with a similar issue in the future.

# SCRAMBLE WORD/PHRASE
# IMPORTS
import random
# VARIABLES
test_words_list = ["dark", "happy holidays", "computer", "I like pie", "dogs love pizza"]
# FUNCTIONS
def scramble_string(string: str, seperate_words = False) -> str:
string = string.lower()
scramble = ""
if seperate_words == False:
"""Remove spaces & scramble all letters together into one string"""
words_list = string.split(" ")          
for word_str in words_list:
word_letter_list = [letter for letter in word_str]    # list of letter in word for each word in words_list
random.shuffle(word_letter_list)
scrambled_word_str = "".join(word_letter_list)
scramble += scrambled_word_str
else:
"""scramble letters in words WITHOUT mixing letters from different words.
List scrambled words in orginal order (with space between)"""
words_list = string.split()
for word in words_list:
scrambled_list = [letter for letter in word]
random.shuffle(scrambled_list)
scrambled_str = "".join(scrambled_list)
scrambled_str += " "                           # Add space between words in string
scramble += scrambled_str
return scramble
# Tests
print(scramble_string(test_words_list[-2]))           # WORKS (returned = "hyppahadsilyo")
print(scramble_string(test_words_list[-1], True))    # WORKS (returned = "sdog eovl zapzi")
# Working Notes (to track & learn from mistakes)
# Error SOURCE: scrambled_list.append(letters_list)   
# Failed Solution(makes scramble a list): scramble = ''.join(str(scrambled_list)[1:-1])  
# Soultion(Error: "sequence item 0: expected str instance, list found") scrambled_list.append("".join(letters_list))
# Error RESOLVED (list of lists of strings given to "".join): scrambled_str = "".join(scrambled_list)