Why templates create reusable prompts in LangChain - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a prompt template with a variable placeholder.

LangChain

from langchain import PromptTemplate

prompt = PromptTemplate(template="Hello, [1]!", input_variables=["name"])

Drag options to blanks, or click blank then click option'

Aage

Bname

Clocation

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a placeholder that is not listed in input_variables.

Mismatching the placeholder name and input variable.

The variable placeholder in the template must match the input variable name, which is 'name' here.

2fill in blank

medium

Complete the code to format the prompt with the variable 'name' set to 'Alice'.

LangChain

formatted_prompt = prompt.format([1]="Alice")

Drag options to blanks, or click blank then click option'

Aname

Bage

Clocation

Dgreeting

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not defined in the template.

Passing the value without specifying the variable name.

The format method requires the variable name 'name' to replace the placeholder in the template.

3fill in blank

hard

Fix the error in the code by choosing the correct input variable name for the template.

LangChain

prompt = PromptTemplate(template="Your favorite color is [1].", input_variables=["color"])

Drag options to blanks, or click blank then click option'

Acolour

BfavColor

Cfavorite_color

Dcolor

Attempts:

3 left

💡 Hint

Common Mistakes

Using British spelling 'colour' instead of 'color'.

Using camelCase or different variable names.

The placeholder and input variable must match exactly; 'color' is correct here.

4fill in blank

hard

Fill both blanks to create a prompt template with two variables and format it correctly.

LangChain

prompt = PromptTemplate(template="Hello, [1]! You are [2] years old.", input_variables=["name", "age"])
formatted = prompt.format([1]="Bob", [2]=30)

Drag options to blanks, or click blank then click option'

Aname

Bage

Cusername

Dyears

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names between template and format method.

Using variables not declared in input_variables.

The placeholders and input variables must match: 'name' and 'age' are correct.

5fill in blank

hard

Fill all three blanks to create a reusable prompt template with three variables and format it with values.

LangChain

prompt = PromptTemplate(template="Dear [1], your order [2] will arrive on [3].", input_variables=["customer", "order_id", "delivery_date"])
message = prompt.format([1]="Anna", [2]="12345", [3]="Monday")

Drag options to blanks, or click blank then click option'

Acustomer

Border_id

Cdelivery_date

Darrival_time

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names not declared in input_variables.

Mismatching placeholder names and format keys.

The placeholders and input variables must match exactly: 'customer', 'order_id', and 'delivery_date'.

Practice

1. Why do templates help when creating prompts in Langchain?

easy

A. They make prompts run faster by skipping processing

B. They automatically generate new prompts without any input

C. They let you reuse the same prompt structure with different data

D. They replace the need for any user input

Solution

1. Step 1: Understand what templates do

   Templates use placeholders to create a prompt structure that can be filled with different values.

2. Step 2: Recognize the benefit of reusing prompts

   This means you write the prompt once and reuse it many times with different data, saving time and keeping consistency.

3. Final Answer:

   They let you reuse the same prompt structure with different data -> Option C

4. Quick Check:

   Reusable prompt structure = D [OK]

Hint: Templates reuse prompt text with placeholders [OK]

Common Mistakes:

• Thinking templates generate prompts without input
• Believing templates remove need for user input
• Assuming templates speed up prompt execution

2. Which of the following is the correct way to define a prompt template with a placeholder named name in Langchain?

easy

A. PromptTemplate(template="Hello, %name%!")

B. PromptTemplate(template="Hello, $name!")

C. PromptTemplate(template="Hello, <name>!")

D. PromptTemplate(template="Hello, {name}!")

Solution

1. Step 1: Recall Langchain placeholder syntax

   Langchain uses curly braces {} to mark placeholders in prompt templates.

2. Step 2: Match the correct syntax

   The correct syntax for a placeholder named 'name' is {name}, so the template string should be "Hello, {name}!".

3. Final Answer:

   PromptTemplate(template="Hello, {name}!") -> Option D

4. Quick Check:

   Curly braces for placeholders = A [OK]

Hint: Use curly braces {} for placeholders in templates [OK]

Common Mistakes:

• Using $ or % instead of curly braces
• Using angle brackets <> which are invalid
• Forgetting to wrap the template string in quotes

3. Given the following code snippet, what will be the output?

from langchain import PromptTemplate

template = PromptTemplate(template="Hello, {name}!")
output = template.format(name="Alice")
print(output)

medium

A. Hello, Alice!

B. Hello, {name}!

C. Hello, name!

D. Error: Missing placeholder value

Solution

1. Step 1: Understand the template and format call

   The template has a placeholder {name}. The format method fills this with the value "Alice".

2. Step 2: Determine the printed output

   Replacing {name} with "Alice" results in the string "Hello, Alice!" which is printed.

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Placeholder replaced by 'Alice' = B [OK]

Hint: format() fills placeholders with given values [OK]

Common Mistakes:

• Printing the template string without formatting
• Confusing placeholder name with literal text
• Expecting an error when all placeholders are provided

4. What is wrong with this Langchain prompt template code?

from langchain import PromptTemplate

template = PromptTemplate(template="Welcome, {user}!")
output = template.format(username="Bob")
print(output)

medium

A. The placeholder name in template and format do not match

B. The template string is missing curly braces

C. The format method is not supported in PromptTemplate

D. The import statement is incorrect

Solution

1. Step 1: Compare placeholder and format argument names

   The template uses {user} but the format call uses username="Bob" which does not match.

2. Step 2: Understand placeholder replacement rules

   Since the placeholder {user} is not provided a value, formatting will fail or leave it unchanged.

3. Final Answer:

   The placeholder name in template and format do not match -> Option A

4. Quick Check:

   Placeholder and argument names must match = A [OK]

Hint: Match placeholder names exactly in format() call [OK]

Common Mistakes:

• Using different names for placeholders and values
• Forgetting curly braces in template
• Assuming format() is unsupported

5. You want to create a reusable prompt template that asks for a user's favorite color and hobby. Which approach best uses templates to keep your prompts consistent and easy to update?

hard

A. Use separate templates for color and hobby and combine them manually

B. Create a template with placeholders {color} and {hobby}, then fill them each time you ask

C. Write a new prompt string every time with the user's answers included

D. Hardcode the questions and ignore user input for simplicity

Solution

1. Step 1: Identify the goal of reusability and consistency

   Using one template with placeholders for both color and hobby lets you reuse the prompt easily and keep it consistent.

2. Step 2: Compare options for maintainability

   Writing new strings each time or splitting templates adds complexity and risks inconsistency.

3. Final Answer:

   Create a template with placeholders {color} and {hobby}, then fill them each time you ask -> Option B

4. Quick Check:

   Single template with placeholders = C [OK]

Hint: Use one template with multiple placeholders for related data [OK]

Common Mistakes:

• Writing new prompt strings every time
• Splitting related questions into separate templates
• Ignoring user input to simplify prompts