"""
Lecture 5/6 
Demo'd code exploring lists and different ways
to define and use them.
"""

# While not suggested, you can mix types in a list
lst = [1, '0.5', -2, min, 0.5, 'Curly', [0, 1, 2]]
# Note above that `lst` is an ok variable name
# to refer to some arbitrary list; don't use 
# `list` as a variable name (it's a built-in Python
# type) and use more meaningful variable names if
# appropriate.

# Average temps from Sept. 30 to Oct. 6 in Pasadena
temps = [87.4, 87.5, 82.9, 80.3, 79.5, 78.3, 76.3]

# Accessing elements
temps[0]
temps[2]
temps[-1]
# temps[len(temps) - 1]

# Two ways to use brackets: creating and accessing 
[1, 2, 3, 4, 5][2] # (rarely see this in practice)

days_in_months = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]



days_in_months[0] 
days_in_months[1] 

# How do we get the number of days in October (Month 10)? (2 ways)

# Can also access from the end
days_in_months[-1] # last element (Dec.)
days_in_months[-2] # second-to-last element (Nov.)

# Careful, accessing at an index outside of the bounds gives an error
# days_in_months[len(days_in_months)] # last element: days_in_months[11]
# days_in_months[-13] # first element: days_in_months[-12]

# Modifying lists
nums = [-1, 12, 4, 5, 2]
nums[2] = 8 

# How is this different than the string sequence?
s = 'Lorem'
s[0] = 'l'

nums[2] = 2 * nums[2]
# nums[2] = 2 * 4
# nums[2] = 8
nums[2] *= 2
nums[2] = nums[2] * 2

# Operators on lists
# Concatenation with +
[1, 2, 3] + [4, 5, 6]

# Replication with *
[1, 2, 3] * 3
[1, 2, 3] * 0
[1, 2, 3] * -1 

# List functions
len([1, 2, 3])
len(days_in_months)
days_in_months[int(len(days_in_months) / 2) + 2]
# days_in_months[len(days_in_months) // 2 + 2]

# Can convert another sequence to a list (if possiible)
curly_lst = list('Curly')
# And can convert a list back to aa string (delimited by the 
# string .join is called on). Don't overuse though (e.g.
# don't take a string, convert to list, then join back to a string).
curly_str = ''.join(curly_lst)

# We can add to the end of a list with append
nums = []
nums.append(1)
nums.append(2)
nums.append(3)
nums.append(2)

# To find an element index (location) in a list, use the index method
nums.index(2) # index of the _first_ occurrence of the value 2
# error if value isn't in list
# nums.index(4)

nums = [1, 2, 3, 2, 4]
# If there are multiple occurrences of the value, returns the earliest index
nums.index(2)

# To remove an element, use the remove method
nums.remove(2)
# Only removes first element of the list, and error if not found

# Summing a list
sum(temps)

# Finding the average
sum(temps) / len(temps)

# Reversing a list 
nums.reverse()

# Aliasing
# Assigning a list to a variable does not copy that list.
# Instead, it is a reference to that value, and the value
# update will be seen in both variables (show debugger)
nums = [-1, 12, 4, 5, 2]
nums2 = nums
nums2[0] = 0
print(nums2)
print(nums)

# Compare this with strings and ints
x = 1
y = x
x *= 2
print(x, y)

s1 = 'foo'
s2 = 'bar'
s1 *= 2
print(s1, s2)

# Can also make copies if you don't want aliasing
nums2 = nums.copy()
nums2[0] = 0
print(nums2)
print(nums)

# Slicing
# Can select a group of elements in the list
days_in_months = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
# lst[start:end] -> returns a list holding items between [start, end)
days_in_months[1:] # everything after the first element
days_in_months[1:3] # elements 2nd to 3rd
days_in_months[:-4] # elements beginning to 4th-to-last element
# Can also change a sequence of items using splice
nums = [1, 2, 3, 4, 5]
nums[1:3] = [0, 0]

cities = ['Pasadena', 'Los Angeles', 'Sacramento', 
          'San Diego', 'San Francisco']

for city in cities:
  print(city)
  print('---')

temp = 85
if temp > 72:
  print('Hot!')
elif temp > 80:
  print('Hotter!')


rna_seq = 'ugcca'
# expected result: ['a', 'c', 'g', 'g', 'u']
# make a list result (rna_lst)
for ch in rna_seq:
  # add the complement of ch in the list
  if ch == 'a':
    ...
  elif ch == 'c':
    ...
  elif ch == 'g':
    ...
  else: # ch == 'u'
    ...
    
  


# Can get the count of items in a list
nums.count(2)

# And sort them. Remember that lists are mutable!
nums.sort()

# list_cyu.py Exercise

# Practice with functions
# Exercise: Write a function get_median that returns the median of the list
# Assume the list is an odd-length (why?) 
def get_median(lst):
  temp = lst.copy()
  temp.sort()
  middle_index = len(temp) // 2
  return temp[middle_index]

nums = [1, -1, 4, 18, 2, 0, 5]
median = get_median(nums)

# Exercise (home): Write a function get_range that returns the 
# range of the list, where range = max - min
def get_range(lst):
  return 0
  
# Exercise (at home): Write a function vowel_count that returns a list of vowel counts
def vowel_count(s):
  # e.g. vowel_count('bOwie') should return:
  # [0, 1, 1, 1, 0]
  # representing counts for:
  # ['a', 'e', 'i', 'o', 'u']
  return 0

# Nested lists
# The following puzzles are from Reading 8, practicing nested lists
# List Puzzle 1 
# Can you explain why the following code 
# behaves the way it does? Try with the VSCode debugger or PythonTutor!
lst1 = [1, 2, 3]
lst2 = [lst1, lst1]
print(lst2)
lst1[0] = 42
print(lst1)
print(lst2)

# List Puzzle Part 2
# What does the following code do?
lst2[0][0] = 1
print(lst2)
print(lst1)

# List Puzzle Part 3
# What does the following code do?
lst1 = [1, 2, 3]
lst2 = lst1 * 3
print(lst2)
lst3 = [lst1] * 3
print(lst3)
lst1[0] = 42
print(lst1)
print(lst2)
print(lst3)
lst1 = [1, 2, 3]
lst2 = [lst1, lst1]
print(lst2)
lst1[0] = 42
print(lst1)
print(lst2)

  
# Challenge problem (on your own)
def mystery(lst, x, y):
  lst[lst[y]] = lst[x]
  lst[x] = y 

nums = [1, -2, 6, 4, 0, 3, 0, 9, 12]
mystery(nums, 2, 4) # use the debugger to "step into" this call
# What does nums look like here?
nums