- The main goal of this (and maybe the following) week
- Lists (arrays)
- Loops
Lists are used to store multiple items in a single variable.
Lists are created using square brackets.
my_list = ["pesho", "gosho", "ivan"]Lists can be of any type
list1 = ["pesho", "gosho", "ivan"]
list2 = [1, 2, 3, 4, 5]
list3 = [False, True, False]Types can even be mixed
my_list = ["pesho", 34, True, 42, "gosho"]List items are ordered, changeable, and allow duplicate values.
List items are indexed, the first item has index [0], the second item has index [1] etc.
my_list = ["pesho", "gosho", "ivan", 42]
first_item = my_list[0]
second_item = my_list[1]
third_item = my_list[2]
# You can count backwards - starting from the last item
last_item = my_list[-1]List items are changeable
my_list = ["pesho", "gosho", "ivan", 42]
my_list[1] = "ralica"
print(my_list) # >>> ['pesho', 'ralica', 'ivan', 42]All lists have length - to determine how many items a list has, use the len() function.
my_list = [] # an empty list
print(len(my_list)) # >>> 0
my_list = ["pesho", "gosho", "ivan", 42]
print(len(my_list)) # >>> 4To insert a new list item, without replacing any of the existing values, we can use the insert() method.
The insert() method inserts an item at the specified index.
my_list = ["pesho", "gosho", "ivan"]
my_list.insert(2, "ralica")
print(my_list) # >>> ['pesho', 'gosho', 'ralica', 'ivan']To add a new list item to the end of the list you can use the append() method.
my_list = ["pesho", "gosho", "ivan"]
my_list.append(10)
print(my_list) # >>> ['pesho', 'gosho', 'ivan', 10]The pop() method removes the specified index.
my_list = ["pesho", "gosho", "ivan"]
my_list.pop(1)
print(my_list) # >>> ['pesho', 'ivan']The pop() method without an argument will remove the last item
my_list = ["pesho", "gosho", "ivan"]
my_list.pop()
print(my_list) # >>> ['pesho', 'gosho']With the while loop we can execute a set of statements as long as a condition is True.
i = 1
while i < 6:
print(i)
i += 1 # same as `i = i + 1`The loop can be ‘stuck’ in so-called endless loop if the condition is always True.
i = 1
while True:
print(i)
i += 1 # same as `i = i + 1`With the break statement we can stop the loop even if the while condition is true.
i = 1
while i < 6:
if i == 4:
# when i becomes equal to 4 then loop will exit
break
print(i)
i += 1 # same as `i = i + 1`With the continue statement we can stop the current iteration, and continue with the next.
i = 1
while i < 6:
if i % 2:
# when i is even the loop will continue with the next iteration
continue
print(i)
i += 1 # same as `i = i + 1`We can loop through lists
my_list = ["pesho", "gosho", "ivan"]
i = 0
while i < len(my_list):
print(my_list[i])
i += 1 # same as `i = i + 1`A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a
string).
my_list = ["pesho", "gosho", "ivan"]
for name in my_list:
print(name)With the break statement we can stop the loop before it has looped through all the items.
my_list = ["pesho", "gosho", "ivan"]
for name in my_list:
if name == "gosho":
break
print(name)With the continue statement we can stop the current iteration of the loop, and continue with the next.
my_list = ["pesho", "gosho", "ivan"]
for name in my_list:
if name == "gosho":
continue
print(name)The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and
stops before a specified number.
range(10)
# range(start, stop, step)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]To loop through a set of code a specified number of times, we can use the range() function
for x in range(10):
print(x)Sum of a list. Given this list of numbers:
numbers = [80, 23, 78, 56, 14, 73, 4, 46, 79, 9, 55, 84, 65, 20, 27]Write a python program that will calculate their sum.
713
Average of a list. Given this list of numbers:
numbers = [3, 56, 97, 43, 25, 72, 74, 40, 82, 84, 24, 51, 28, 87, 81]Write a python program that will calculate the average (mean).
56.46666666666667
Min and Max in a list. Given this list of numbers:
numbers = [18, 32, 72, 100, 7, 74, 17, 45, 42, 66, 86, 79, 23, 54, 35]Write a python program that will find the max and min numbers in that list.
Max: 100
Min: 7
Find the second biggest number. Given this list of numbers:
numbers = [13, 17, 85, 49, 66, 25, 46, 65, 4, 23, 3, 71, 44, 12, 50, 62, 33, 82, 47, 36]Write a python program that will find the second biggest number in that list.
82
Find if list contains a given numbers. Given this list of numbers, and a number to look for:
numbers = [68, 65, 30, 87, 21, 17, 96, 70, 64, 34, 14, 90, 86, 31, 29, 40, 59, 23, 25, 95, 60, 85, 42, 37, 57, 18, 27,
77, 36, 75, 4, 5, 38, 63, 76, 81, 53, 24, 62, 98, 83, 55, 67, 1, 7, 92, 8, 51, 52, 61, 3, 56, 97, 12, 71, 20,
16, 26, 50, 10, 73, 89, 88, 49, 28, 100, 13, 47, 69]
number = 42Write a python program that will print: Number found if the number is in the numbers list. Otherwise,
print: Not found...
Number found
Find if a list has duplicated numbers. Given these lists of numbers:
numbers_01 = [13, 17, 85, 49, 66, 25, 46, 65, 4, 23, 3, 71, 44, 12, 50, 62, 33, 82, 47, 36]
numbers_02 = [89, 75, 78, 84, 27, 82, 63, 72, 6, 41, 77, 35, 92, 90, 8, 72, 21, 74, 48, 97, 42, 28, 45, 84, 22, 63, 4,
74, 6, 70, 13, 30]
numbers_03 = [54, 32, 37, 35, 66, 48, 15, 27, 48, 82, 38, 96, 58, 95, 13, 64, 67, 58, 94, 90, 10, 11, 36, 29, 36, 25,
20, 94, 25, 74, 42, 30, 74, 52, 12, 39, 70, 30, 14, 91, 92, 55, 11, 6, 55, 36, 92, 84, 11, 90, 76, 11, 18,
32, 1, 16, 73, 66, 21, 86, 49, 53, 33, 25]
numbers_04 = [68, 65, 30, 87, 21, 17, 96, 70, 64, 34, 14, 90, 86, 31, 29, 40, 59, 23, 25, 95, 60, 85, 42, 37, 57, 18,
27, 77, 36, 75, 4, 5, 38, 63, 76, 81, 53, 24, 62, 98, 83, 55, 67, 1, 7, 92, 8, 51, 52, 61, 3, 56, 97, 12,
71, 20, 16, 26, 50, 10, 73, 89, 88, 49, 28, 100, 13, 47, 15]Write a python program that will print: Duplicates found for each of these lists if any of the numbers can be found
twice or more in the same list. Otherwise, print: The list is free of duplicates
List #1: The list is free of duplicates
List #2: The list is free of duplicates
List #3: Duplicates found
List #4: The list is free of duplicates
Find if a string contains a character. Given this string and the character to look for:
string = "the quick brown fox jumps over the lazy dog"
character = "q"Write a python program that will print: Character found if the character is in the string. Otherwise,
print: Not found...
Character found
Find if a string contains a substring. Given this string and the substring to look for:
string = "the quick brown fox jumps over the lazy dog"
substring = "brown fox"Write a python program that will print: Substring found if the substring is in the prime string. Otherwise,
print: Not found...
Substring found
Check for Balanced Brackets in a string
example for balanced : "(b * b) - (4 * a * c)"
example for not balanced : "b) * b)"
string_01 = "Thi(s is) (a very annoy)ing ((se(n)tence)) with some (brackets)"
string_02 = "This i(s a v)ery ann)oy(ing sentence w((i)th so)me (b(r(a(pesho(k(e(t(s))))))))"Write a python program that will print for each strings (01 and 02): Balanced brackets if the brackets in the string
are well-balanced. Otherwise, print: Not balanced brackets.
String #1: Balanced brackets
String #2: Not balanced brackets