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Why Python for Robotics?

Python is a powerful language that is readable, expressive, and widely used in robotics for sensor interaction, motor control, and decision logic:

• Read sensor values (e.g., distance, light, temperature)

• Store those values in variables

• Compute decisions (e.g., “stop”, “turn”, “slow down”)

• Send commands to actuators (e.g., wheels, servos)

Before controlling movement, you must understand how Python stores, evaluates, and manipulates data. These concepts: variables, data types & expressions, are the foundations of all Python programs.

Data Types First… Then We Will Talk About Variables

• A Value is one of the basic pieces of data that a Python program can work with, such as a number or string. Every value in Python belongs to a Data Type — a category that tells Python what kind of value it is and how it behaves.

• Python, like any other structured language has values in form of  Variables, defined as Data Types and they are used to resolve Expressions.

• Data Types represents the kind of value that tells what operations can be performed on a particular data. 

• Since everything is an object in Python programming, Data Types are actually classes and variables are instances (objects) of these classes.

Common Data Types

• Integer (int)

  • Whole numbers without decimals.

  • Example: 42, -7

• Floating-point number (float)

  • Numbers with a decimal point.

  • Example: 3.14, 0.0

• String (str)

  • Text enclosed in quotes.

  • Example: "Forward", 'STOP'

Integers: int vs long?

In Python 3 (modern Python)

• There is NO separate long type. (Python 3 merged them)

• int handles all whole numbers

• int = unlimited precision integer

• Small or extremely large — Python manages it automatically

In Python, an int represents any whole number, and Python automatically handles very large values, so there is no separate long type.

x = 10

y = 999999999999999999999

Both are:

type(x) == type(y)  # True

float Data Type

A float is a data type used to store numbers with decimal points.  Floats are commonly used in robotics to represent:

• Sensor distances

• Voltages

• Speeds

• Time measurements

Floats allow more precise measurements than integers, but they can include small rounding errors, so they should be used carefully in comparisons.  Use float whenever measurements are not whole numbers.

float in Robotics

• Floats allow more precise measurements than integers

• But they can include more significant digits and can include small rounding errors

• They should be used carefully in comparisons.  <-- More on this "rounding" in a later LAB

• Use float whenever measurements are not whole numbers.

Floats as Scientific or Engineering Notation:

• Floats may also be in scientific notation, with E or e indicating the power of 10. When a number is really really big or very very small, it is more readable to represent it as an exponent.

• 2.5e2 = 2.5 x 102 = 250

• Big Numbers:

  • 6.02214076e23 is Avogadro’s number, and it is very very big.  You would have to agree that 6.0221407623 or 6.02214076e23 is more readable than 6.0221407600000000000000000000000

  • 4.7e6 rather than 47000000, which might be a resistor value of  4.7MΩ

  • 10e3 rather than 10000, which might be a resistor value of  10KΩ

  • 7e9 = Population of the world is around 7 billion written out as 7000000000

  • 1.08e9 = Approximate speed of light is 1080 million km per hour or 1080000000 km per hour

  • 3.99e13 = Distance from the sun to the nearest star (Proxima Centauri) is 39900000000000 km

• Small Numbers:

  • These exponents can also be negative 2.2e-9 = 2.2 x 10-9 = .0000000022 or 2.2 pF

  • You might also see some small number represented in scientific or engineering notation like: capacitor

    • 2.2e-9 rather than .0000000022, which might be a capacitor value of  2.2 x 10-9 = 2.2 pF

    • 2.4e-3 = Diameter of a grain of sand is 24 ten-thousandths inch or .0024 inch

    • 7.53e-10 = Mass of a dust particle is 0.000000000753 kg

    • 9.1093822e-31 = Mass of an electron is 0.00000000000000000000000000000091093822 kg

    • 4.0e-7 = Length of the shortest wavelength of visible light (violet) is 0.0000004 meters

float in Robotics

• Floats allow more precise measurements than integers

• But they can include more significant digits and can include small rounding errors <-- More on this later

• They should be used carefully in comparisons

• Use float whenever measurements are not whole numbers

Try Some Code In https://www.python.org/shell/ 

Float

>>> pi = 3.14159265359

>>> print(pi)

??? <--What got printed?

>>> type(pi)

??? <--What got printed?

Dividing Numbers Int to Float

>>> x = 10

>>> y= 2

>>> z = x / y

>>> print(z)

??? <--What got printed?

>>> y= 3

>>> z = x / y

>>> print(z)

??? <--What got printed?

Forcing An Integer Divide With //

>>> z=x//y

>>> print(z)

??? <--What got printed?

>>> type(z)

??? <--What got printed?

Big Numbers:

>>> x = 2.5e3

>>> print(x)

??? <--What got printed?

>>> x = 2.5e15

>>> print(x)

??? <--What got printed?

>>> x = 2.5e16

>>> print(x)

??? <--What got printed?

Small Number:

>>> x = 2.2e-3

>>> print(x)

??? <--What got printed?

>>> x = 2.2e-4

>>> print(x)

??? <--What got printed?

>>> x = 2.2e-9

>>> print(x)

??? <--What got printed?

>>>

Python complex Data Types

• In mathematics, a complex number is a number that can be expressed in the form a + bi, where a and b are real numbers, and i is a symbol called the imaginary unit, and satisfying the equation i2 = -1. 

• Because no "real" number satisfies this equation, i was called an imaginary number by René Descartes. 

• For the complex number a + bi, 

  • a is called the real part

  • b is called the imaginary part.

• Typically an imaginary number is used to denote a point location on a Cartesian plane

• Where you have an "x" value and a "y" value.  

• The "x" value is the real part of this number and the "y" is the imaginary.  

• Both numbers are "real" numbers and can be integer or float values.

If we wanted to plot the point x= 3 and y = 7, we could represent this as a complex number:

 my_graf_number = (3+7j)

Python str Data Types

• A string (str) in Python is a sequence of characters enclosed in single quotes ('...') or double quotes ("...").

• Strings are used to store textual information, such as:

• Rover status messages: "MOVING", "STOP"

• Sensor labels: "FrontSensor"

• Logs or debug messages: "Battery low!"

status = "MOVING"

sensor_label = "Front Sensor"

String Variable Objects and the Value Inside

>>> my_snake_sound_variable = 'Hissssssss'

>>> print(my_snake_sound_variable)

??? <--What got printed?

>>> print(type(my_snake_sound_variable))

??? <--What got printed?

• my_snake_sound_variable is a variable object, and the value inside the object is a string "Hisssssss"

• my_snake_sound_variable is a type <class 'str'>

>>> my_char_variable = '25'

>>> print(my_char_variable)

??? <--What got printed?

>>> print(type(my_char_variable))

??? <--What got printed?

>>>

• my_char_variable is a variable object, and the value inside the object is a string "25"

• my_char_variable is a type <class 'str'>

• Was this what you expected? When you put quotes around something, Python tends to think this is a string...

Numeric vs Strings 

>>> x = 42

>>> y = 20

>>> z = x + y

>>> print(z)

??? <--What got printed?

>>> x = 42

>>> y = "20"

>>> z = x + y

>>> print(z)

??? <--What got printed?

• Strings in Python behave like a list of characters:

• Each character in the string has a position (index)

• You can access, slice, or iterate over a string just like a list

greet ="Hello World"
print(greet)
# Access individual characters
print(greet[0])  # 'H'
print(greet[6])  # 'W'
# Slicing
print(greet[1:5])  # 'ello'

• Just like a list, string indexing starts at 0, and negative indices count from the end  (-1 is the last character).

Strings Are Immutable

• Immutable? What does that mean?

• You cannot change a character in place:

greet = "Hello World"

greet[0] = "M" # This will raise an error

• Instead, you create a new string:

greet = "M" + greet[1:]

print(greet)

Python bool Data Types

• A Boolean variable is a type of variable that can only hold two possible values: True or False

• Booleans are commonly used to represent conditions, states, or flags in a program 

• A robot might need to know:

  • If an obstacle is detected

  • If a motor is running

  • If a battery is low

• Using a Boolean variable makes it easy to store, check, and control these conditions

• Boolean - Comparison Operators

  • Equal to (==)

  • Not equal to (!=)

  • Greater than (>)

  • Less than (<)

  • Greater than or equal to (>=)

  • Less than or equal to (<=)

• Note: We are using the "==" operator rather than the "=", because we want a comparison evaluation not an assignment operation. 

>>> 5 == (3 + 2)

??? <--What got printed?

>>> 1 == 2

??? <--What got printed?

>>> "bob" == "Bob"

??? <--What got printed?

>>> x = 9

>>> 6 < x

??? <--What got printed?

True / False 

You can assign a variable with the Boolean value of True or False, and then use these in Loops and Flow Control operations.  We will see examples of that in later lessons.

>>> my_bool_var = True

>>> print(my_bool_var)

??? <--What got printed?

>>> my_bool_var = False

>>> print(my_bool_var)

??? <--What got printed?

Bool - Check If Object Is Detected

Cntl-a, then paste this code:

# Boolean flag to track if obstacle is detected

obstacle_detected = False

# Sensor reading (distance in cm)

distance_front = 15

# Check if an obstacle is close

if distance_front < 20:

    obstacle_detected = True  

# Print the status

print("Obstacle detected?", obstacle_detected)

Re run with distance_front = 22

Python - Let's Do Some Math - Evaluating Expressions

• Evaluating Math and Order of Operations

• Python allows you to perform a variety of mathematical operations on numbers using arithmetic operators. These are essential when working with sensor readings, distances, speeds, or battery levels in robotics.

• Practical Tip for Robotics

  • Use integer division (//) for counts, steps, or discrete units.

  • Use float division (/) for distances, voltages, or precise measurements.

  • Combine multiple operators carefully, and use parentheses to make your logic explicit.

Run This Code - Math In Robotics

# Rover wheel parameters

wheel_speed = 3       # speed in cm/sec

travel_time = 5       # time in seconds

# Calculate distance using multiplication

distance = wheel_speed * travel_time

print("Distance traveled:", distance, "cm")

??? <--What got printed?

Math - Floating Point Precision 

# Battery voltage readings

battery_start = 12.63

battery_current = 11.24

# Subtract to find voltage drop

battery_drop = battery_start - battery_current

print("Battery voltage drop:", battery_drop, "V")

Order Of Operations

• When more than one operator appears in an expression, the order of evaluation depends on the rules of precedence. For mathematical operators, Python follows mathematical convention

• Python follows PEMDAS order of operations:

• Parentheses → Exponents → Multiplication/Division → Addition/Subtraction

• Using parentheses ensures calculations are evaluated correctly

>>> x = 2*3-1

>>> print(x)

??? <--What got printed?

>>> x = 6+4/2

>>> print(x)

??? <--What got printed?

>>> x = 2*(3-1)

>>> print(x)

??? <--What got printed?

>>> x = (6+4)/2

>>> print(x)

??? <--What got printed?

Python - Extra Stuff

• Simultaneous Assignment

  • Python also allows chained assignment, which makes it possible to assign the same value to several variables simultaneously:

>>> x = y = someVar = 42

>>> print(x, y, someVar)

??? <--What got printed?

Text Books, Reference, Tutorials & Other Online Resources: 🤖🚙

Reference, Attribution & Resources:

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Standards Alignments & Objectives:

I’ll work on getting these in, but it’s the last thing I want to work on :-) When I have them updated, I’ll move to the top of the Lesson Plan. 

• NGSS: <list standard numbers>

• California CTE Standards: <list standard numbers>

• Related Instructional Objectives (SWBAT):  <list standard numbers>

• CCSS: nnn, RSIT: nnn, RLST: nnn, WS: nnn, WHSST: nnn, A-CED: nnn, ETS: nnn  <list standard numbers>

• Main Standard:

• Priority standards:

• National Standards:

Resource Attribution:

Sites Referenced or Summarized:

• Text Book - Automate the Boring Stuff with Python, 2nd Edition: Practical Programming for Total Beginners 

• Text Book - Think Python: How to Think Like a Computer Scientist (HTML) 3rd Edition

• Reference Python Class - Python 4 Everyone 

Images:

• https://imgbin.com/png/ZJtzkYZZ/under-construction-png 

What To Fix, Add, Or Change

• add links to w3schools for any text like float()

• Add labs from the presentation