String Formatting#

Introduction #

f-strings are the recommended way to format text and numbers in Python. They allow variables, expressions, and function calls to be embedded directly inside {}.

To create an f-string, add f before the string, and place any variable, expression, or function call inside {}.

x = 1
y = 5

# Display the variables using an f-string
robot.screen.print(f"Position: ({x}, {y})")

# Display a calculation with an f-string
robot.screen.print(f"Sum: {5 + 3}")

# Display the robot's battery capacity with an f-string
robot.screen.print(f"Battery: {robot.get_battery_level()}%")

f-Strings – Embed variables and expressions directly in text.

f”{value}” – Displays variables, expressions, or function calls inside a string.

Formatting Numbers in f-strings – Control how numeric values appear.

:.xf – Sets the number of decimal places to show.
round – Rounds a number to a given number of decimal places.
:, – Adds commas as thousands separators.
:.x% – Converts a decimal to a percentage with x decimal places.
:#x – Formats a number as hexadecimal.
:b – Formats a number as binary.

String Combination – Combine text and values.

f”{value}” – Combine strings and variables in a single expression.
+ operator – Concatenate strings manually with optional type conversion.

String Methods – Change the case of text.

upper() – Converts all characters to uppercase.
lower() – Converts all characters to lowercase.

Substring Checks – Test for presence or position of text.

in – Checks if a word exists in a string.
startswith() – Checks if a string begins with a given value.
endswith() – Checks if a string ends with a given value.

Escape Sequences – Format output with special characters.

\n – Adds a line break (new line).
\t – Adds a tab space between items.

Formatting Numbers in f-strings #

f-strings allow precise control over decimal places, rounding, thousands separators, and more by using the following format specifiers:

Fixed Decimal Places #

.xf controls how many decimal places a number is displayed with.

Usage:
.xf

Parameters	Description
`x`	The amount of decimal places to show.

# Display pi with 2 decimal places
pi = 3.1415926535
robot.screen.print(f"Pi: {pi:.2f}")  # Output: Pi: 3.14

Rounding Numbers #

round rounds numbers outside of an f-string or inside of the {}.

Usage:
round(number, x)

Parameters	Description
`number`	The number to round.
`x`	The amount of decimal places to round to.

# Display a value rounded to only 2 decimal places
value = 5.6789
robot.screen.print(f"{round(value, 2)}")  # Output: 5.68

Thousands Separator #

, inserts commas as thousands separators to make large numbers more readable.

Usage:
,

Parameters	Description
	This format specifier has no parameters.

# Display a large number separated with commas
number = 1234567
robot.screen.print(f"{number:,}")  # Output: 1,234,567

Percentage #

.x% formats decimal values as percentages.

Usage:
.x%

Parameters	Description
`x`	The amount of decimal places to show.

# Display a converted decimal to a percentage
value = 0.875
robot.screen.print(f"{value:.1%}")  # Output: 87.5%

Hexadecimal #

.#x converts numbers to hexadecimal.

Usage:
.#x

Parameters	Description
	This format specifier has no parameters.

# Convert 255 to hexadecimal
number = 255
robot.screen.print(f"{number:#x}")  # Output: 0xff

Binary #

b converts numbers to binary (base 2).

Usage:
b

Parameters	Description
	This format specifier has no parameters.

# Convert 3 to binary
robot.screen.print(f"Binary: {3:b}")  # Output: 11

Combining Strings #

You can combine (or concatenate) strings using two approaches:

Using f-strings #

With f-strings, you can embed variables directly inside {}.

# Display an answer based on the given emotion
emotion = "good"
robot.screen.print(f"I'm {emotion}, you?")

+ Operator #

You can combine strings manually using the + operator.

Note: Non-strings must first be converted to strings using str().

# Display the x and y values
x = 10
y = 20
robot.screen.print("X: " + str(x) + ", Y: " + str(y))

String Methods #

Python provides built-in methods for modifying and checking strings.

upper #

upper converts all letters in a string to uppercase.

Usage:
upper()

Parameters	Description
	This method has no parameters.

message = "vexcode"
robot.screen.print(message.upper())  # Output: VEXCODE

lower #

lower converts all letters in a string to lowercase.

Usage:
lower()

Parameters	Description
	This method has no parameters.

message = "VEXCODE"
robot.screen.print(message.lower())  # Output: vexcode

Checking for Substrings #

in #

in is a keyword that returns a Boolean indicating whether a word exists in a string.

True - The word exists in the string.
False - The word does not exist in the string.

message = "Hey everyone!"
if "Hey" in message:
    robot.screen.print("Hello!")

startswith #

startswith returns a Boolean indicating whether a string begins with a given value.

True - The word starts the string.
False - The word does not start the string.

Usage:
startswith(substring)

Parameters	Description
`substring`	The substring to check inside the string.

message = "AIM Robot"

if message.startswith("AIM"):
    robot.screen.print("AIM first!")

endswith #

endswith returns a Boolean indicating whether a string ends with a given value.

True - The word ends the string.
False - The word does not end the string.

Usage:
startswith(substring)

Parameters	Description
`substring`	The substring to check inside the string.

message = "AIM Robot"

if message.endswith("Robot"):
    robot.screen.print("Robot last!")

Escape Sequences #

Escape sequences are special characters used inside strings to format text output. They are only available for use with the Console.

New Line #

\n moves text to a new line when printing.

# Display text on two lines
print("First line\nSecond line")

Tab Spacing #

\t inserts a tab space between words or numbers,

# Display the quantity of barrels
quantity = 2
print("Barrels:\t", quantity)