CS- Week 6

Python

Python is an easy-to-use, versatile programming language that is an excellent choice for both beginners and industry experts.
Unlike C, Python is an interpreted language, so you don't need to compile the program separately. Instead, the program is run in the Python interpreter.

The code that displays the message "hello, world" written in C is represented in Python as follows:

print("hello, world")

Notice that there are no semicolons and no libraries required. In Python, it is possible to implement relatively simple codes that are more complex in C language.

Variable declaration is simplified in Python. For example, in C, a variable can be defined as int counter = 0; is announced as In Python, it is not required to declare the type of the variable: counter = 0.

In Python, it is not necessary to specify the data types, the interpreter can determine it based on the value of the variable. The following data types are commonly used in Python:

bool

• float
• int
• str
• Types long and double like C do not exist in Python. Python decides for itself which data type to use for large and small numbers.

Other data types used in Python include:

range

• list
• tuple
• dict
• set
• Each of these data types can be implemented in C, but Python has the ability to implement them in a simpler way.

Conditional operators

---

When using conditional operators in Python, parentheses - () are optional.

Python uses

indentation

instead of {}.
else if is used in C, Python uses elif instead. If, elif and else operators are followed by a colon :


in C || The logical operator

"or"

from cs50 import get_int

x = get_int("x ni kiriting: ")
y = get_int("y ni kiriting: ")

if x < y:
    print("x soni y sonidan kichik")
elif x > y:
    print("x soni y sonidan katta")
else:
    print("x soni y soniga teng")

is replaced by or in Python.

Python uses str instead of char, which allows you to work with a single character or string.

Repetition operators

from cs50 import get_string
s = get_string("Ma'lumotlar o'zgartirilishiga rozimisiz? ")

if s == "Y" or s == "y":
    print("Ha.")
elif s == "N" or s == "n":
    print("Yo'q.")

---

The syntax of iteration operators

(loops)

in Python is very similar to C, but simpler and more understandable.

Using the while loop, we display the message "meow":

print("hello, world")

We can further simplify the above code by using

for loop:

from cs50 import get_int

x = get_int("x ni kiriting: ")
y = get_int("y ni kiriting: ")

if x < y:
    print("x soni y sonidan kichik")
elif x > y:
    print("x soni y sonidan katta")
else:
    print("x soni y soniga teng")

Python automatically increments the value of in here.
We can also write the above code as:

from cs50 import get_string
s = get_string("Ma'lumotlar o'zgartirilishiga rozimisiz? ")

if s == "Y" or s == "y":
    print("Ha.")
elif s == "N" or s == "n":
    print("Yo'q.")

This approach modularizes the code.

---

list

Using

List we can store many values ​​in one variable. We can refer to the elements of lists through the index.

i = 0
while i < 3:
    print("meow")
    i += 1

using the len() method, we determine the length of the listing, that is, the number of elements.
We calculate the sum of the elements of the list consisting of numbers using the sum() method.

A loop can be used to retrieve values ​​from the user:

for i in range(3):
    print("meow")

The

append method adds a new value to the list.

To search for a value in a list in Python, you can use a loop or use a shorter method:

def main():
    meow(3)


def meow(n):
    for i in range(n):
        print("meow")


main()

The

in operator checks whether the given value exists in the list.

---

Dictionary

Dictionary are key-value pairs that speed up the search process.

scores = [72, 73, 33]

# O'rtacha qiymatni topamiz
average = sum(scores) / len(scores)
print(f"Average: {average}")

people[name] retrieves the corresponding value from the dictionary.
The dictionary lookup speed is typically O(1).

---

Command Line Arguments

In Python, command line arguments can be used using the sys library:

from cs50 import get_int

# Foydalanuvchidan qiymatlarni kiritishni so'raymiz
scores = []
for i in range(3):
    score = get_int("Score: ")
    scores.append(score)

# O'rtacha qiymatni topamiz
average = sum(scores) / len(scores)
print(f"Average: {average}")

argv - contains a list of arguments, the first element of which is the file name.
We display all arguments:

# Ismlar ro'yxati
names = ["Carter", "David", "John"]

# Foydalanuvchidan ism kiritishni so'raymiz
name = input("Name: ")

# Ro'yxatdan qidiramiz
if name in names:
    print("Topildi")
else:
    print("Topilmadi"

We use certain exit codes (exit status) to indicate the state in which the program ended:

from cs50 import get_string

people = {
    "Carter": "+1-617-495-1000",
    "David": "+1-617-495-1000",
    "John": "+1-949-468-2750",
}

# Kiritilgan ismni qo'yxatdan qidiramiz
name = get_string("Name: ")
if name in people:
    print(f"Telefon raqam: {people[name]}")
else:
    print("Topilmadi")

sys.exit() returns an exit code (for example, 0 means that the program completed successfully).

This article uses CS50x 2024 source.

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