DeepLearningAI - ChatGPT Prompt Engineering for Developers - Iterative

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When I’ve been building applications with

large language models, I don’t think I’ve ever come to the prompt that

I ended up using in the final application on my first attempt.

And this isn’t what matters. As long as you have a good process

to iteratively make your prompt better, then you’ll

be able to come to something that works

well for the task you want to achieve.

You may have heard me say that when I train a machine learning model,

it almost never works the first time. In fact, I’m very surprised if the first

model I train works. I think we’re prompting, the odds

of it working the first time is maybe

a little bit higher, but as he’s saying, it doesn’t matter if the

first prompt works. What matters most is the process for getting

to the prompts that work for your application.

So with that, let’s jump into the code and let me show

you some frameworks to think about how to

iteratively develop a prompt. Alright, so if you’ve taken

a machine learning class with me, before you

may have seen me use a diagram saying that with

machine learning development, you often have an idea and

then implement it. So write the code, get the

data, train your model, and that gives you an experimental result. And you

can then look at that output, maybe do error analysis, figure out

where it’s working or not working, and then

maybe even change your idea of exactly what problem

you want to solve or how to approach

it, and then change your implementation and run another experiment and so

on, and iterate over and over to get

to an effective machine learning model. If you’re not familiar with machine learning

and haven’t seen this diagram before, don’t worry about it,

not that important for the rest of this presentation. But

when you are writing prompts

to develop an application using an OOM, the process can be

quite similar where you have an idea for what you want to

do, the task you want to complete, and you can then

take a first attempt at writing a prompt

that hopefully is clear and specific and maybe,

if appropriate, gives the system time to think,

and then you can run it and see what result you get.

And if it doesn’t work well enough the first time, then

the iterative process of figuring out why the instructions,

for example, were not clear enough or why it didn’t give

the algorithm enough time to think, allows you

to refine the idea, refine the prompt, and so on, and to

go around this loop multiple times until you

end up with a prompt that works for your application. This too

is why I personally have not paid as

much attention to the internet articles that say

30 perfect prompts, because I think there probably isn’t a perfect

prompt for everything under the sun. It’s more important that

you have a process for developing a good

prompt for your specific application. So let’s look

at an example together in code. I have here the starter

code that you saw in the previous videos,

have been port open AI and port OS. Here we get the open

AI API key, and this is the same helper function that you

saw as last time.


I’m going to use as the running example in

this video the task of summarizing a fact

sheet for a chair. So let me just paste that in here. Feel

free to pause the video and read this more carefully

in the notebook on the left if you want. But here’s a

fact sheet for a chair with a description saying it’s part of

a beautiful family of mid-century inspired, and so on. Talks about the construction,

has the dimensions, options for the chair,

materials, and so on. Comes from Italy.

So let’s say you want to take this fact sheet and help a marketing

team write a description for an online retail


as follows, and I’ll just…

and I’ll just paste this in,

so my prompt here says your task is to help a marketing

team create the description for retail

website or product based on a techno fact sheet,

write a product description, and so on. Right? So this is my

first attempt to explain the task to the large-language

model. So let me hit shift enter, and

this takes a few seconds to run,

and we get this result. It looks like it’s

done a nice job writing a description, introducing a stunning mid-century inspired

office chair, perfect edition, and so on, but when

I look at this, I go, boy, this is really long. It’s done a

nice job doing exactly what I asked it to, which is start

from the technical fact sheet and write a

product description.

But when I look at this, I go, this is kind of long.

Maybe we want it to be a little bit shorter.

So I have had an idea. I wrote a prompt, got the result.

I’m not that happy with it because it’s too

long, so I will then clarify my prompt and say

use at most 50 words to try to give better guidance on

the desired length of this, and let’s run it again.

Okay, this actually looks like a much nicer short

description of the product, introducing a mid-century

inspired office chair, and so on, five you just, yeah, both

stylish and practical. Not bad.

And let me double check the length that this is. So I’m

going to take the response, split it according to where

the space is, and then you’ll print out the length. So it’s 52 words.

Actually not bad.

Large language models are okay, but not that great

at following instructions about a very precise word count,

but this is actually not bad. Sometimes it will print

out something with 60 or 65 and so on words, but it’s

kind of within reason. Some of the things you

Let me run that again. But these are different

ways to tell the large-language model what’s the length of the output

that you want. So this is one, two, three. I count

these sentences. Looks like I did a pretty good job. And then

I’ve also seen people sometimes do things like, I don’t know, use at

most 280 characters. Large-language models, because of the way they

interpret text, using something called a tokenizer, which I won’t talk about.

But they tend to be so-so at counting characters. But

let’s see, 281 characters. It’s actually surprisingly close. Usually a

large-language model doesn’t get it quite

this close. But these are different ways they can play

with to try to control the length of the output that you

get. But then just switch it back to use at most

50 words.

And that’s that result that we had just now.

As we continue to refine this text for our website,

we might decide that, boy, this website isn’t

selling direct to consumers, it’s actually intended to sell

furniture to furniture retailers that would

be more interested in the technical details of the chair and the

materials of the chair. In that case, you can

take this prompt and say, I want to modify this prompt to get it to

be more precise about the technical details.

So let me keep on modifying this prompt.

And I’m going to say,

this description is intended for furniture retailers,

so it should be technical and focus on materials,

products and constructs it from.

Well, let’s run that.

And let’s see.

Not bad. It says, coated aluminum base

and pneumatic chair.

High-quality materials. So by changing the prompt, you

can get it to focus more on specific characters, on

specific characteristics you want it to. And

when I look at this, I might decide, hmm, at the end of the description,

I also wanted to include

the product ID. So the two offerings of this chair,

SWC 110, SOC 100. So

maybe I can further improve this prompt.

And to get it to give me the product IDs,

I can add this instruction at the end of the description,

include every 7 character product ID

in the technical specification. And let’s run it

and see what happens.

And so it says, introduce you to our mid-century

inspired office chair, shell colors, talks about plastic coating

aluminum base,

practical, some options,

talks about the two product IDs. So this looks pretty good.

And what you’ve just seen is a short example of the iterative

prompt development that many developers will

go through.

And I think a guideline is, in the last video,

you saw Yisa share a number of best practices. And so what I

usually do is keep best practices like that in mind,

be clear and specific, and if necessary,

give the model time to think. With those in mind, it’s

worthwhile to often take a first attempt at

writing a prompt, see what happens, and then go from there

to iteratively refine the prompt to get closer

and closer to the result that you need. And

so a lot of the successful prompts that

you may see used in various programs was

arrived at an iterative process like this. Just

for fun, let me show you an example of an even

more complex prompt that might give you a sense of what ChatGPT

can do, which is I’ve just added a few extra

instructions here. After description, include a

table that gives the product dimensions, and then

you’ll format everything as HTML. So let’s run


And in practice, you would end up with a prompt like this,

really only after multiple iterations. I don’t think I know anyone

that would write this exact prompt the first

time they were trying to get the system

to process a fact sheet.

And so this actually outputs a bunch of HTML. Let’s

display the HTML to see if this is even valid

HTML and see if this works. And I don’t actually know it’s going to

work, but let’s see. Oh, cool. All right. Looks like a rendit.

So it has this really nice looking description of

a chair. Construction, materials, product dimensions.

Oh, it looks like I left out the use at most 50 words instruction,

so this is a little bit long, but if you want that,

you can even feel free to pause the video, tell it to be more

succinct and regenerate this and see what results you get.

So I hope you take away from this video that prompt development

is an iterative process. Try something,

see how it does not yet, fulfill exactly what you want,

and then think about how to clarify your instructions,

or in some cases, think about how to give

it more space to think, to get it closer to

delivering the results that you want. And I think the

key to being an effective prompt engineer isn’t

so much about knowing the perfect prompt, it’s about

having a good process to develop prompts that are

effective for your application. And in

this video I illustrated developing a prompt using

just one example. For more sophisticated applications, sometimes you

will have multiple examples, say a

list of 10 or even 50 or 100 fact sheets, and iteratively

develop a prompt and evaluate it against a

large set of cases.

But for the early development of most applications,

I see many people developing it sort of the way

I am with just one example, but then for more mature applications,

sometimes it could be useful to evaluate prompts against

a larger set of examples, such as to test

different prompts on dozens of fact sheets to

see how this average or worst case performance

is on multiple fact sheets. But usually you end up doing

that only when an application is more mature and you have to

have those metrics to drive that incremental last few

steps of prompt improvement.

So with that, please do play with the Jupyter code notebook

examples and try out different variations and see

what results you get. And when you’re done, let’s go

on to the next video where we’ll talk about one very common use of large

language models in software applications, which is to

summarize text.