Variables and dynamic content in LangChain - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a variable that stores a user's name.

LangChain

user_name = [1]

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

AAlice

Bname

C"Alice"

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around text

Using variable names instead of text

Variables that store text must be enclosed in quotes.

2fill in blank

medium

Complete the code to insert a variable into a prompt string using f-string syntax.

LangChain

prompt = f"Hello, [1]! How can I help you today?"

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

Aname

Buser_name

C"user_name"

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around the variable inside the f-string

Using a different variable name than defined

Inside an f-string, variables are used without quotes to insert their values.

3fill in blank

hard

Fix the error in the code to correctly create a prompt with dynamic content.

LangChain

prompt = f"Your order number is [1]."

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

Aorder-num

B"order_number"

CorderNumber

Dorder_number

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the variable name

Using a variable name with invalid characters

The variable name must match exactly and be used without quotes inside the f-string.

4fill in blank

hard

Fill both blanks to create a dictionary with variable keys and values.

LangChain

data = { [1]: [2] }

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

A"user_id"

Buser_id

C12345

D"12345"

Attempts:

3 left

💡 Hint

Common Mistakes

Using variables without quotes as keys

Using numbers without quotes when strings are needed

Dictionary keys as strings need quotes, and values can be strings too.

5fill in blank

hard

Fill all three blanks to create a prompt template with variables and a condition.

LangChain

prompt = f"Hello, [1]! Your balance is [2]. [3]"

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

Auser_name

Bbalance

C"Please pay soon."

D"Thank you for your payment.%"

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around variable names inside the f-string

Forgetting to quote the message string

Use variables user_name and balance inside the f-string, and add a message as a string.

Practice

1. What is the main purpose of using variables in a Langchain PromptTemplate?

easy

A. To create multiple templates at once

B. To insert changing information into the text dynamically

C. To store the final output text permanently

D. To make the template text static and unchangeable

Solution

1. Step 1: Understand the role of variables in templates

   Variables are placeholders that allow parts of the text to change based on input.

2. Step 2: Connect variables to dynamic content

   Using variables lets you insert different values each time you use the template, making it dynamic.

3. Final Answer:

   To insert changing information into the text dynamically -> Option B

4. Quick Check:

   Variables = dynamic content insertion [OK]

Hint: Variables let text change based on input values [OK]

Common Mistakes:

• Thinking variables make text static
• Confusing variables with final output storage
• Believing variables create multiple templates automatically

2. Which of the following is the correct way to define a PromptTemplate with variables in Langchain?

easy

A. PromptTemplate(template="Hello {name}", input_variables=name)

B. PromptTemplate(template="Hello name", input_variables=[name])

C. PromptTemplate(template="Hello {name}", input_variables=["name"])

D. PromptTemplate(template="Hello {name}", variables=["name"])

Solution

1. Step 1: Check the syntax for defining variables

   The input_variables parameter must be a list of strings naming the variables used in the template.

2. Step 2: Match the template placeholders with variable names

   The template uses curly braces around variable names like {name} to mark where to insert values.

3. Final Answer:

   PromptTemplate(template="Hello {name}", input_variables=["name"]) -> Option C

4. Quick Check:

   Correct syntax = PromptTemplate(template="Hello {name}", input_variables=["name"]) [OK]

Hint: Use curly braces and list of strings for variables [OK]

Common Mistakes:

• Forgetting quotes around variable names
• Using wrong parameter name like variables instead of input_variables
• Not using curly braces in template

3. Given the code:

template = PromptTemplate(template="Hello {user}, today is {day}.", input_variables=["user", "day"])
result = template.format(user="Alice", day="Monday")
print(result)

What will be printed?

medium

A. Hello Alice, today is Monday.

B. Hello {user}, today is {day}.

C. Hello user, today is day.

D. Error: Missing variables

Solution

1. Step 1: Understand how format fills variables

   The format method replaces {user} with "Alice" and {day} with "Monday".

2. Step 2: Predict the final string after formatting

   The placeholders are replaced, so the printed string is "Hello Alice, today is Monday."

3. Final Answer:

   Hello Alice, today is Monday. -> Option A

4. Quick Check:

   format replaces variables correctly = Hello Alice, today is Monday. [OK]

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

Common Mistakes:

• Printing template string without formatting
• Confusing variable names with values
• Expecting an error when variables are provided

4. What is wrong with this code snippet?

template = PromptTemplate(template="Hi {name}", input_variables=["name"])
result = template.format(nam="Bob")
print(result)

medium

A. input_variables should be a string, not a list

B. The template string is missing curly braces

C. format method cannot be used with PromptTemplate

D. The variable name in format is misspelled, causing a KeyError

Solution

1. Step 1: Compare variable names in template and format call

   The template expects variable "name" but format uses "nam" which is incorrect.

2. Step 2: Understand the error caused by mismatch

   This mismatch causes a KeyError because "name" is not provided in format arguments.

3. Final Answer:

   The variable name in format is misspelled, causing a KeyError -> Option D

4. Quick Check:

   Variable name mismatch = KeyError [OK]

Hint: Check variable names match exactly in template and format [OK]

Common Mistakes:

• Assuming format ignores missing variables
• Thinking input_variables must be a string
• Believing format method is invalid here

5. You want to create a PromptTemplate that dynamically inserts a user's name and their favorite color, but if the color is not provided, it should default to "blue". Which approach correctly handles this dynamic content with a default value?

hard

A. Use input_variables=["name", "color"] and call format with color="blue" if missing

B. Define template with {name} and {color}, but omit color from input_variables to default it

C. Use input_variables=["name"] only and write template as "Hello {name}, your color is blue"

D. Set input_variables=["name", "color"] and use a conditional expression inside template like {color or 'blue'}

Solution

1. Step 1: Understand how to provide default values

   Langchain's PromptTemplate requires all variables listed in input_variables to be provided when formatting.

2. Step 2: Provide default value in code when calling format

   By including color in input_variables and passing color="blue" if missing, you ensure the template fills correctly.

3. Final Answer:

   Use input_variables=["name", "color"] and call format with color="blue" if missing -> Option A

4. Quick Check:

   Default values handled in format call = Use input_variables=["name", "color"] and call format with color="blue" if missing [OK]

Hint: Provide all variables; set defaults when calling format [OK]

Common Mistakes:

• Omitting variables from input_variables to default
• Trying to use Python expressions inside template strings
• Hardcoding default text instead of using variables