Cheatsheets
Build Chatbots with Python - Introduction to Python and Chatbots

Build Chatbots with Python - Introduction to Python and Chatbots

Getting Started with Python and Comments

What Are Comments?

Comments are notes in your code that the computer ignores. They help you understand and explain what your code does.

                                

# This is a comment on a single line
user = "JDoe" # This is a comment next to code

Basic Math in Python

Python can perform basic math operations like addition, subtraction, multiplication, and division.

                                

# Basic math operations
result = 10 + 30  # Addition
result = 40 - 10  # Subtraction
result = 50 * 5   # Multiplication
result = 16 / 4   # Division
result = 25 % 2   # Modulo (remainder)
result = 5 ** 3  # Exponentiation (5 raised to the power of 3)

Using += to Add

The += operator adds a value to a variable and updates it. It can also be used to join strings.

                                

# Using += operator
counter = 0
counter += 10  # Increases counter by 10
message = "Part 1"
message += " Part 2"  # Joins two strings

What Are Variables?

Variables store data such as numbers or text. You can change their values as needed.

                                

# Example variables
user_name = "codey"
user_id = 100
verified = False
# Changing a variable's value
points = 100
points = 120

Understanding Modulo %

The % operator gives the remainder of a division. It helps determine how many times a number can be divided by another with a remainder.

                                

# Using modulo operator
zero = 8 % 4  # Remainder is 0
nonzero = 12 % 5  # Remainder is 2

Working with Whole Numbers (Integers)

Integers are whole numbers without decimals. They can be positive, negative, or zero.

                                

# Examples of integers
chairs = 4
tables = 1
broken_chairs = -2
sofas = 0
# Examples of non-integers
lights = 2.5
left_overs = 0.0

Joining Strings Together

Strings (text) can be combined using the + operator to make longer messages.

                                

# Combining strings
first = "Hello "
second = "World"
result = first + second  # Joins strings
long_result = first + second + "!"

Common Errors in Python

Errors occur when there are mistakes in your code, like typos or incorrect syntax.

                                

if False ISNOTEQUAL True:
                  ^
SyntaxError: invalid syntax

Division by Zero Error

Dividing a number by zero is not allowed and results in an error.

                                

# Division by zero error
numerator = 100
denominator = 0
bad_results = numerator / denominator
ZeroDivisionError: division by zero

Using Strings

Strings are sequences of characters. They can be enclosed in single or double quotes.

                                

# Examples of strings
user = "User Full Name"
game = 'Monopoly'
longer = "This string is broken up \
over multiple lines"

Syntax Errors Explained

Syntax errors happen when the code doesn’t follow Python’s rules, such as using incorrect operators or missing symbols.

                                

age = 7 + 5 = 4
File "", line 1
SyntaxError: can't assign to operator

Name Errors

NameErrors occur when you try to use a variable that doesn’t exist or was mistyped.

                                

misspelled_variable_name
NameError: name 'misspelled_variable_name' is not defined

Working with Decimal Numbers (Floats)

Floating point numbers (floats) include decimals, representing non-integer numbers.

                                

# Examples of floats
pi = 3.14159
meal_cost = 12.99
tip_percent = 0.20

Using the print() Function

The print() function displays text or numbers on the screen.

                                

print("Hello World!")
print(100)
pi = 3.14159
print(pi)

Understanding Functions

What Are Lambda Functions?

Lambda functions are small, unnamed functions used for simple operations in a single line of code.

                                

# Defining a lambda function
add_one = lambda x: x + 1
print(add_one(5))  # Output will be 6

Function Parameters Explained

Parameters are variables in functions that accept input values when the function is called.

                                

# Function with parameters

def write_a_book(character, setting, special_skill):
  print(character + " is in " + 
        setting + " practicing her " + 
        special_skill)

Using Multiple Parameters

Functions can take multiple inputs (parameters) to perform more complex tasks.

                                

# Function with multiple parameters

def ready_for_school(backpack, pencil_case):
  if (backpack == 'full' and pencil_case == 'full'):
    print("I'm ready for school!")

Defining and Using Functions

Functions are blocks of reusable code that perform specific tasks. They can be defined once and used multiple times.

                                

# Defining a function

def my_function(x):
  return x + 1
# Using the function
print(my_function(2))      # Output: 3
print(my_function(3 + 5))  # Output: 9

Indentation in Functions

Indentation shows which lines of code are part of the function. Indent all code inside a function.

                                

# Function with indentation

def testfunction(number):
  print("Inside the function")
  sum = 0
  for x in range(number):
    sum += x
  return sum
print("Outside the function")

Calling Functions

To use a function, call it by writing its name followed by parentheses.

                                

doHomework()

Returning Values from Functions

Functions can return values using the return keyword. These values can be used later in the program.

                                

# Function that returns a value

def sales(grocery_store, item_on_sale, cost):
  print(grocery_store + " is selling " + item_on_sale + " for " + cost)
sales("The Farmer’s Market", "toothpaste", "$1")

Using Keyword Arguments

Keyword arguments specify which value goes to which parameter by name, not just by position.

                                

def findvolume(length, width, depth):
  print("Length = " + str(length))
  print("Width = " + str(width))
  print("Depth = " + str(depth))
  return length * width * depth

# Calling the function with keyword arguments
volume = findvolume(width=2, depth=3, length=4)
print(f"Volume: {volume}")

Using Default Parameters

Default parameters have preset values that are used if no other value is provided.

                                

# Function with default parameters

def favorite_color(color="blue"):
  print("My favorite color is " + color)
# Calling the function
favorite_color()
favorite_color("green")

Control Flow Basics

Using If Statements

If statements run code only if a condition is true.

                                

# If statement example
if 5 > 3:
  print("5 is greater than 3")

Using If-Else Statements

If-else statements provide an alternative block of code to execute if the condition is false.

                                

# If-else statement example
if 5 > 10:
  print("5 is greater than 10")
else:
  print("5 is not greater than 10")

Using Elif Statements

Elif (else if) allows checking multiple conditions.

                                

# Elif statement example
score = 85
if score >= 90:
  print("Grade A")
elif score >= 80:
  print("Grade B")
else:
  print("Grade C")

For Loops Basics

For loops repeat a block of code for each item in a sequence, such as a list or range.

                                

# For loop example
for i in range(5):
  print(i)

While Loops Basics

While loops continue to execute code as long as a condition remains true.

                                

# While loop example
count = 0
while count < 5:
  print(count)
  count += 1

Breaking Out of Loops

Use the break statement to stop a loop before it finishes all iterations.

                                

# Breaking out of a loop
for i in range(10):
  if i == 5:
    break
  print(i)

Using Continue in Loops

Use the continue statement to skip the rest of the loop's code and start the next iteration.

                                

# Continue statement example
for i in range(10):
  if i % 2 == 0:
    continue
  print(i)  # Only odd numbers will be printed

Programming Cheatsheets: Quick Reference for Productivity

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