Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skillsβperfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Understanding `range(i, j)`
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Let's begin our discussion about the `range()` function. When we use `range(i, j)`, we start at `i` and generate numbers up to but not including `j`. Can anyone tell me what we call the last number generated?
It's `j - 1`, right?
Exactly! So if we have `range(3, 7)`, we get the numbers 3, 4, 5, and 6. Remember, it stops right before `j`.
What if I just write `range(5)`?
Great question! In that case, it will be interpreted as `range(0, 5)`, producing 0 through 4. So, the starting point defaults to 0.
Using Steps in `range()`
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Now, letβs examine the third parameter, the step value, `k`. If you want to skip numbers, how would you use it?
By adding a third argument in `range()`?
Correct! For instance, `range(2, 10, 2)` produces 2, 4, 6, 8. In this case, we count by twos. What happens if we set our step to a negative value?
We would count backwards, like `range(10, 0, -2)`?
Exactly right! And it will generate 10, 8, 6, 4, 2. As a reminder, make sure the starting point is greater than the end point!
Empty Sequences with `range()`
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Letβs talk about generating empty sequences. What causes this to happen when using `range()`?
If the starting number is larger than `j` when counting up?
Correct again! If we write something like `range(10, 5)`, we wonβt get any values because we canβt count from 10 down to 5 in an increment of 1.
And what about going the other way?
Good point! If the start is below the end point for a negative step, we also get an empty sequence. This might seem confusing, but just remember: you can't cross `j`!
`range` vs Lists
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
How does the result of `range()` differ from lists?
Isnβt `range` just a list of numbers from the start to the end?
Not quite! In Python 3, `range` creates a range object and not a full list. Can anyone explain how we can convert it into a list?
By using the `list()` function, right?
Exactly! For example, `list(range(5))` gives [0, 1, 2, 3, 4]. This distinction is necessary for understanding how they can be used in loops.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section provides a comprehensive overview of the range() function in Python, clarifying how it generates sequences of numbers. Key concepts include the starting point, step value, and how it handles upper limits, as well as differences between Python 2 and Python 3 in terms of the outputs of range().
Detailed
Detailed Summary
The range() function in Python is a powerful tool for generating sequences of numbers. It is primarily used for looping a specific number of times in for loops. The basic syntax, range(i, j, k), generates numbers starting from i, incrementing by k, and stopping before j. If only one argument, j, is provided, the range starts at 0 and goes up to j-1. The function also allows for counting backwards when a negative step value is used.
Additionally, this section clarifies that the results from range() are not lists in Python 3, contrasting it with Python 2. To convert the generated sequence into a list, one must use the list() function. This understanding of range() is significant for managing sequences effectively, especially in relation to lists and iterations. Correct interpretation of index bounds is essential in programming to avoid errors such as generating empty sequences.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding the Range Function
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
We have seen the range function which produces a sequence of values. In general, if we write range(i, j), we get the sequence i, i + 1 up to j - 1. Quite often we want to start with 0. So, if we will give only one argument, if we just write range(j), this is seen as the upper bound and the lower bound is 0.
Detailed Explanation
The range function generates a series of numbers, starting from a specified value (or defaulting to 0) and going up to, but not including, another specified value. For example, range(3) will produce the numbers 0, 1, and 2. It's important to note that the range function is inclusive of the starting number but exclusive of the ending number.
Examples & Analogies
Think of a countdown from 3 to 0. If you are counting down for a game, you would say '3, 2, 1' (which corresponds to range(3)). You're starting at 0 and stopping before you say '3' because you never say '3' during your countdown.
Skip Values with a Step
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Often we may want to generate a sequence where we skip by a value other than 1. This can be done using a third argument. The third argument tells the range function to skip every k items.
Detailed Explanation
When we want to generate number sequences with a specific interval, we use a third parameter in range. For instance, range(1, 10, 2) will produce 1, 3, 5, 7, and 9. Here, we start at 1 and increment by 2 each time until we reach the upper bound of 10.
Examples & Analogies
Imagine you are on a hopping game where you skip every other step to reach your destination. Instead of going '1, 2, 3', you jump over every second number, which means your sequence would be '1, 3, 5' as you hop along.
Going Down with Negative Steps
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Having a step also allows us to count down. If we say range(i, j, -1), we will start with the value which is bigger than the final value and produce a decreasing sequence.
Detailed Explanation
The range function can also be used to create a decreasing sequence by providing a negative step. For example, range(10, 0, -1) will produce the numbers 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. This way, we can effectively count backwards.
Examples & Analogies
If you were on a stairway and wanted to step down each stair backward, you would count down from 10 to 1 as you descend each step. You wouldn't count below 0, just as range will stop at just above your lower limit.
Understanding Range and List Differences
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
It is often confusing to new programmers that range(i, j) is actually from i to j - 1 and not to j itself. This makes it easier to process lists, where positions are numbered starting from 0.
Detailed Explanation
The range function does not include the upper limit in the generated sequence, unlike what many might expect. This design decision aligns well with how list indices work in Python, allowing developers to iterate over list indices seamlessly. For instance, if a list has a length of 5, the valid indices would be 0 to 4, which can be efficiently generated using range(len(your_list)).
Examples & Analogies
Imagine you have a row of 5 boxes labeled from 0 to 4. If someone asks you to go to box 5, you can't because that box doesnβt exist! Just like in Python, when we say range(5), we're effectively saying, 'Give me all the boxes from 0 to 4', but not including box 5.
Generating Lists from Ranges
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
It is possible to use range to generate a list using the function list. If I want the list of numbers 0 to 4, I can use list(range(0, 5)). This is an example of type conversion.
Detailed Explanation
In Python, range creates a sequence of numbers, which isn't inherently a list. However, by wrapping the range function call inside list(), we can create an actual list. This allows us to manipulate the output more conveniently, using list-specific operations.
Examples & Analogies
Consider making a collection of toys (a list) starting with some numbers. If you say range(0,5), you are just imagining the numbers. But when you say list(range(0,5)), you're assembling those numbers into a box of toys that you can then play with, much more easily than just numbers alone.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Range Syntax:
range(i, j)produces values fromitoj-1. -
Default Start: Using
range(j)defaults torange(0, j). -
Step Parameter: The third argument
kallows skipping values;range(i, j, k). -
Empty Sequences: Generated by improper bounds.
-
Type Difference: In Python 3,
range()is not a list; needs conversion to list.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
Example of Range:
range(3, 8)produces sequence [3, 4, 5, 6, 7]. -
Negative Range:
range(10, 0, -2)produces sequence [10, 8, 6, 4, 2]. -
Using List Function: We convert the range using
list(range(5))to get [0, 1, 2, 3, 4].
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
-
With
rangeitβs plain to see, start and stop, count with glee! Just remember less than j, thatβs how we play every day.
π Fascinating Stories
-
Imagine a train starting at station
iand stopping before reaching stationj. With every halt, it collects or drops passengersβa smooth and orderly flow just like therange()function!
π§ Other Memory Gems
-
Remember βS for Start, J for Journeyβ, which means to count from start
ito just beforej.
π― Super Acronyms
R.A.N.G.E
- Results from `i` to `j`
- Adjust steps with `k`
- Never go beyond `j`
- Generate sequences Easily.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: range()
Definition:
A built-in Python function that generates a sequence of numbers, defined by start, stop, and step parameters.
-
Term: Upper Bound
Definition:
The maximum value that the range function will generate, exclusive.
-
Term: Step Value
Definition:
The amount by which the next number in the sequence will increase or decrease.
-
Term: Empty Sequence
Definition:
A sequence with no elements generated due to the defined bounds in
range(). -
Term: Type Conversion
Definition:
The process of converting one data type into another using functions like
list.