We will write a Python program that makes a numbered list of our favorite vacation spots. It will look like this:
1. Paris
2. Tokyo
3. Rome
This helps us learn how to use a 'loop' to count and print things in order!
PY-1.1-BP7-MQ02
Our Goal: Make a Numbered List!
Check Your Work
Before we start, let's run the tests to see what we need to fix.
Run this command in your terminal:
pytest module-1.1/blueprint-7/quest-02
What you should see:
- ❌
test_prints_numbered_vacation_list
Write Your Code
Now, let's write our Python code in main.py! You'll be working inside the print_dream_vacations function. Remember, we want to make a numbered list.
Here are some helpful code examples:
1. How to use a for loop to go through a list:
my_fruits = ["apple", "banana", "cherry"]
for fruit in my_fruits:
print(fruit)
# Output:
# apple
# banana
# cherry
2. How to use range() with a for loop to count:
for i in range(3): # i will be 0, 1, 2
print(i)
# Output:
# 0
# 1
# 2
3. How to make a numbered list (remember to add 1 to i!):
items = ["Pen", "Book", "Eraser"]
for i in range(len(items)):
# i starts at 0, so we add 1 to make it start from 1
print(f"{i + 1}. {items[i]}")
# Output:
# 1. Pen
# 2. Book
# 3. Eraser
4. How to show something on the screen (print):
print("This is a message.")
my_variable = "Hello!"
print(my_variable)
Check Your Work Again
Now, let's run the tests again to see if your code works.
Run this command in your terminal again:
pytest module-1.1/blueprint-7/quest-02
What you should see:
- ✅
test_prints_numbered_vacation_list
Documentation
# Python Fundamentals Refresher
## Functions with Parameters
Functions are blocks of reusable code. Parameters are like placeholders for values that a function needs to do its job.
* **Defining a function:**
```python
def greet(name: str, greeting: str):
# Function code uses name and greeting
print(f"{greeting}, {name}!")
```
* **Calling a function:**
```python
greet("Alice", "Hello")
# Output: Hello, Alice!
```
* **Formatting Strings (f-strings):**
A convenient way to embed expressions inside string literals.
* `f"{variable}"`: Inserts the value of `variable`.
* `f"{float_variable:.2f}"`: Formats a floating-point number to two decimal places.
## Looping with `range()`
`for` loops are used to repeat a block of code multiple times. `range()` generates a sequence of numbers.
* **Basic loop:**
```python
for i in range(3): # i will be 0, 1, 2
print(i)
# Output:
# 0
# 1
# 2
```
* **Using the loop variable for numbered lists:**
`range(len(my_list))` iterates through indices of a list.
```python
items = ["Apple", "Banana", "Cherry"]
for i in range(len(items)):
# i starts at 0, so add 1 for 1-based numbering
print(f"{i + 1}. {items[i]}")
# Output:
# 1. Apple
# 2. Banana
# 3. Cherry
```
## Running Scripts
The `if __name__ == "__main__":` block:
Code inside this block only runs when the script is executed directly (e.g., `python your_script.py`), not when it's imported as a module into another script.
```python
def setup():
print("Setting up...")
def run_program():
print("Running program logic...")
if __name__ == "__main__":
print("Script is being run directly.")
setup()
run_program()
Turtle Graphics
1. Setting Up the Canvas (Screen)
The turtle module draws on a window called the "screen".
- Get the screen:
import turtle screen = turtle.Screen() - Set screen size:
screen.setup(width=600, height=400) # Set window dimensions - Set background color:
screen.bgcolor("lightblue") # Use color names or hex codes - Control screen updates (for faster drawing):
Turn off updates before complex drawing, turn on and update when finished.
screen.tracer(0) # Turn off updates # ... drawing code ... screen.update() # Show the drawing screen.tracer(1) # Turn updates back on (optional, often done implicitly by done()) - Keep the window open:
turtle.done() # Or screen.mainloop()
2. The Turtle (Pen)
The "turtle" is the cursor that draws on the screen. You can have multiple turtles.
- Create a Turtle:
artist = turtle.Turtle() - Hide the Turtle icon:
artist.hideturtle() - Set Speed:
Speed can be 1-10 (slowest to fastest) or 0 (no animation, instant drawing).
artist.speed(0) # Fastest artist.speed(5) # Medium speed - Set Pen Color / Fill Color:
artist.color("red") # Sets both pen and fill color artist.pencolor("blue") # Sets only pen color artist.fillcolor("green")# Sets only fill color - Set Pen Size (Thickness):
artist.pensize(3) # Set pen thickness to 3 pixels - Pen Control:
- Lift the pen (stop drawing when moving):
artist.penup() - Put the pen down (start drawing when moving):
artist.pendown()
- Lift the pen (stop drawing when moving):
3. Movement and Drawing
Commands to move the turtle and draw lines or shapes. The screen's center is (0, 0).
- Go to a Specific Position:
Move the turtle to coordinates (x, y). Draws a line if the pen is down.
artist.goto(100, 50) # Move to x=100, y=50 - Move Forward/Backward:
Move the turtle in its current direction.
artist.forward(100) # Move 100 units forward artist.backward(50) # Move 50 units backward - Turning:
Change the turtle's direction.
artist.left(90) # Turn left by 90 degrees artist.right(45) # Turn right by 45 degrees artist.setheading(0) # Set direction to 0 degrees (East) # 0: East, 90: North, 180: West, 270: South - Drawing Shapes (Examples):
- Square:
# Assuming pen is down and turtle is at a corner facing along an edge side = 50 for _ in range(4): artist.forward(side) artist.left(90) - Circle:
Draws a circle with the given radius. The turtle's current position is the bottom of the circle if facing East.
radius = 30 artist.circle(radius)
- Square:
4. Filled Shapes
Draw shapes that are filled with a solid color.
- Set Fill Color:
Use
fillcolor()or thecolor()command (which sets both pen and fill).artist.fillcolor("blue") - Start and End Fill:
Call
begin_fill()before drawing the shape, andend_fill()after the shape is complete.artist.fillcolor("yellow") artist.begin_fill() # ... drawing commands for the shape (e.g., square, circle, polygon) ... artist.end_fill()
5. Drawing with Functions
Organize your drawing code into functions for reusability.
- Defining a drawing function:
A function can take parameters like position (x, y), size, or color to make it flexible. It often takes the turtle object itself as a parameter.
def draw_dot_at(t, x, y, dot_color, dot_size): t.penup() t.goto(x, y) t.pendown() t.dot(dot_size, dot_color) # Draws a filled circle - Calling a drawing function:
my_turtle = turtle.Turtle() draw_dot_at(my_turtle, 100, 100, "purple", 20) # Draw a purple dot draw_dot_at(my_turtle, -50, 0, "orange", 10) # Draw an orange dot
6. Drawing Multiple Shapes with Loops
Use loops to draw the same shape multiple times at different locations or with variations.
- Looping through coordinates:
Store positions in a list and iterate through the list.
positions = [(100, 100), (-50, 0), (0, -150)] my_turtle = turtle.Turtle() my_turtle.speed(0) # Draw fast for pos_x, pos_y in positions: # Call a drawing function for each position draw_dot_at(my_turtle, pos_x, pos_y, "green", 15) - Calculating positions in a loop:
Use the loop counter to calculate coordinates.
my_turtle = turtle.Turtle() my_turtle.speed(0) for i in range(5): # Draw 5 circles x = -200 + i * 100 # Space circles 100 units apart horizontally y = 0 my_turtle.penup() my_turtle.goto(x, y - 20) # Position for circle bottom (radius 20) my_turtle.pendown() my_turtle.circle(20)
7. Adding Text Labels
Use the write() method to display text on the canvas.
- Writing text:
The text is written at the turtle's current position.
artist.penup() artist.goto(0, 150) # Move to position for text artist.color("black") # Set text color artist.write("My Map Title", align="center", font=("Arial", 16, "bold")) write()parameters:arg: The string to write.move(optional, boolean): If True, the turtle moves to the end of the text. Default is False.align(optional, string): Alignment of the text relative to the turtle's position ("left", "center", or "right"). Default is "left".font(optional, tuple): A tuple(name, size, style).nameis a font family string (e.g., "Arial", "Courier", "Times New Roman").sizeis an integer font height.styleis a string ("normal", "bold", "italic").
