Python — Basic Review before diving deeper 01

Want to recall the memory of Python easily?

6 min readApr 18, 2023

This is the note taken while I was learning Python “again”, hope it helps you too.
There are additional links in the article for you to understand further information.

❤️Good Resources

Bro code | Python full course
ZeroToMastery | Pyhton

How to print out?

There are three ways.

age = 18
print("You are", age, "years old.")
print("You are " + str(age) + " years old.")
print(f"You are {age} years old")

Variables

int
float
string
boolean

age = 18  # integer
gpa = 3.5  # float
name = 'Apple'  # string
dessert = "cake"
grade = 'D'  # string
isValid = True  # boolean

print(f"Your age is {age}.")
print(f"GPA is {gpa}.")
print(f"Name is {name}.")
print(f"Favorite dessert is {dessert}.")
print(f"Grade is {grade}.")
print(f"isValid is {isValid}.")

Multiple values in one line

a, b, c = 1, 2, 3

Typecasting

Manually convert a variable from one data type to another.

int()
str()
float()
bool()

For example (Explicit)

age = 18  # integer

print(type(age))

age = float(age) # float

print(type(age))

Implicit cast

a = 8
b = 4
c = 2.0

ans1 = a / b
ans2 = a / c

print(ans1)
print(type(ans1))
print(ans2)
print(type(ans2))

User Input

name = input("What's your name?")
age = input("How old are you?")

print(f"Heyyya {name},")
print(f"You are {age} years old.")

Input value was string by default.

name = input("What's your name?")
age = input("How old are you?")
age = age + 1 # error

print(f"Heyyya {name},")
print(f"You are {age} years old.")

Correct way is below.

name = input("What's your name?")
age = float(input("How old are you?"))
age = age + 1 # error

print(f"Heyyya {name},")
print(f"You are {age} years old.")

Math

arithmetic operators

The comment in each section is same as the next line.
i.e. apple = apple + 1 is as same as apple += 1

apple = 5

# Addition
# apple = apple + 1
apple += 1

print(apple)

# Substraction
# apple = apple - 1
apple -= 1

print(apple)

# Multiplication
# apple = apple * 2
apple *= 2

print(apple)

# Division
# apple = apple / 2
apple /= 2

print(apple)

# Power
# apple = apple**2
apple **= 2

print(apple)

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Math module

import math

print(math.pi)
print(math.e)

Built-in Functions

a = 3.14
b = -3

num1 = round(a)
num2 = abs(b)
num3 = pow(2, 3)

print(num1)
print(num2)
print(num3)

Exercises

import math

# area
r = float(input("Enter one number: "))
area = math.pi * r

print(area)

Hypotenuses

import math

# hypotenuses
a = float(input("Enter one side:"))
b = float(input("Enter another side:"))
c = math.sqrt(pow(a, 2) + pow(b, 2))

print(f"Side C = {c}")

if statement

if
elif
else

if <expression>:
  <statement>
elif <expr>:
  <statement>
else:
  <statement>

More info can be seen | here

expression can be conditional( age < 18), boolean, values.

age = float(input("Enter your age: "))

if age >= 18:
  print("You are allowed to play the roller coaster.")
else:
  print("You cannot enter the facility.")

isValid = True

if isValid:
  print("You are allowed to play the roller coaster.")
else:
  print("You cannot enter the facility.")

# True
if 1 == 1:
  print("You are allowed to play the roller coaster.")
else:
  print("You cannot enter the facility.")

not

isValid = True

if not isValid:
  print("You are allowed to play the roller coaster.")
else:
  print("You cannot enter the facility.")

While loop

num = int(input("Enter a # bewtween 1 to 5:"))

while num < 1 or num > 5:
  print(f"{num} is not valid.")
  num = int(input("Enter a # bewtween 1 to 5:"))

print(f"The # is {num}")

not

when you need a solution to quit.

desc = input("Type something:(q to quit):")

while not desc == "q":
  print(f"You description is  {desc}.")
  desc = input("Type something:(q to quit):")

If you notice, some questions are repeated.

Python doesn’t have do-while loop,
like what’s said in this article — https://www.freecodecamp.org/news/python-do-while-loop-example/

Do While in C,

#include <stdio.h>
 
int main(void)
 {
   int i = 10;
   do {
      printf("the value of i: %i\n", i);
      i++;
      }
  while( i < 20 );
 }

This is how you can achieve the same effect manually.

secret_word = "python"
counter = 0

while True:
    word = input("Enter the secret word: ").lower()
    counter = counter + 1
    if word == secret_word:
        break
    if word != secret_word and counter > 7: 
        break

Let’s get rid of redundant lines.

for loop

You can iterate over a range, string, sequences, etc.
— bro code

for i in range(1, 11):
  print(i)

print("Weeeeeeeee🎆")

Another usage,

for i in range(1, 11, 3):
  print(i)

print("Weeeeeeeee🎆")

continue & break

for i in range(1, 40):
  if i == 13:
    continue
  elif i == 17:
    break # stop here
  else:
    print(i)

Nested loop

A loop within another loop(s).

rows = int(input("Enter the # of rows: "))
columns = int(input("Enter the # of columns: "))

for i in range(rows):
  for j in range(1,columns):
    print(j, end=" ")
  print() # break the line

If you didn’t add end = “ ”(There is a space between each number per row.

rows = int(input("Enter the # of rows: "))
columns = int(input("Enter the # of columns: "))

for i in range(rows):
  for j in range(1, columns):
    print(j)
  print()