Python3 Cheatsheet: The Basis

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Date created: Dec 15 2021

Last modified: Dec 18 2021

Things to remember

If-else

name = "Guido van Rossum"

if name == "Le Dao": # part 1 (can standalone)
    print("My little world!.")
elif name == "Guido van Rossum": # part 2 (can be multiple)
    print("He is the creator of Python programming language.")
else: # part 3 (must be only one)
    print("Just a person exists on this planet.")

Loop

x = 1
while x <= 10:
    print("Guido van Rossum.")
    x += 1

# infinity loop
while True:
    # do something.
    break # to break this loop if needed
# print "I love you" 10 times.
for i in range(10):
    print("I love you.")

# loop through a list.
my_num = [5, 7]
for num in my_num:
    # do everything with every single num.

Logical operators

Python logical operators: and, or, not. You can use them to combine conditional statements.

gpa = 3.99

if gpa > 3.2 and gpa <= 4:
    print("You have a high GPA. Ya. That's it.",
            "A high score doesn't mean anything.",
            "If you can't solve problems or help others, you suck.")

Function

Function in Python can return anything. There is no need to specify the return type of function.

def say_hello():
    print("Hello, World!")
def say_hello(name):
    print("Hello,", name)

say_hello("Donald J Trump") # output: Hello, Donald J Trump
def sum(a, b):
    return a + b

# call
print(sum(5, 7)) # output: 12
print(sum("7", "9")) # output: "79", funny, right?

Class

Examples say a thousand words.

class Person:
    # constructor
    def __init__(self, name, dob, sex):
        # the first argument ("self") represents the current object.
        # The name of the first argument can be anything. But use "self" to make
        # others happy.
        self.name = name
        self.dob = dob
        self.sex = sex

    # Define methods (A method is a function that an instance of a class calls
    # it (obj.method_name))
    # It is humanity. Don't be shy.
    def eat(self, food):
        print(f"{self.name} is eating {food}.")
    def sleep(self, hour):
        print(f"{self.name} is sleeping about {hour} hour(s).")
    def make_love(self, person, duration):
        print(f"{self.name} is making love with {person.name} in {duration}",
        "minutes.")
    def shit(self):
        print(f"{self.name} is shitting.")
    def __str__(self): # define a string to print when print(obj) called.
        return f"My name is {self.name}. My birthday is {self.dob}."
# use of the class Person
tai = Person(name="Tai", dob="05/05/2000", sex="Male")
dao = Person(name="Dao", dob="05/05/2000", sex="Female")

print(tai) # print the value that returned from __str__
# output: My name is Tai. My birthday is 05/05/2000.

tai.eat("Apple") # output: Tai is eating Apple.
dao.eat("Banh trang tron") # output: Dao is eating Banh trang tron.
tai.make_love(dao, 90) # output: Tai is making love with Dao in 90 minutes.

Now, your turn.

What chapters do you need to include in future documents?

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