For expressions for transformation in Terraform - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a list of doubled numbers using a for expression.

Terraform

output "doubled" {
  value = [for num in var.numbers : num [1] 2]
}

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

A/

B*

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of * will add 2 instead of doubling.

Using / or - will not double the numbers.

The for expression multiplies each number by 2 using the * operator.

2fill in blank

medium

Complete the code to create a map of instance names to their IDs using a for expression.

Terraform

output "instance_map" {
  value = {for inst in var.instances : inst.name => inst.[1]
}

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

Aname

Btype

Cid

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using inst.name as value duplicates the key.

Using inst.type or inst.count are not valid for IDs.

The for expression maps instance names to their IDs using inst.id.

3fill in blank

hard

Fix the error in the for expression to filter only even numbers.

Terraform

output "even_numbers" {
  value = [for n in var.numbers : n if n [1] 2 == 0]
}

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

A+

B*

C/

D%

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or * will not filter even numbers.

Using / returns a quotient, not remainder.

The modulo operator % checks if a number is even by testing remainder 0.

4fill in blank

hard

Fill both blanks to create a map of server names to their IP addresses, filtering only active servers.

Terraform

output "active_servers" {
  value = {for s in var.servers : s.[1] => s.[2] if s.active}
}

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

Aname

Bip

Cid

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using id or status instead of name or ip.

Not filtering by active status.

The map uses server name as key and IP as value, filtering active servers.

5fill in blank

hard

Fill all three blanks to create a map of uppercase user names to their emails, filtering users with verified emails.

Terraform

output "verified_user_emails" {
  value = {for user in var.users : user.[1].[2]() => user.[3] if user.email_verified}
}

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

Aname

Bupper

Cemail

Dlower

Attempts:

3 left

💡 Hint

Common Mistakes

Using lower() instead of upper() for names.

Using email_verified as key instead of filtering condition.

The map uses uppercase user names as keys and emails as values, filtering verified emails.

Practice

1. What does a for expression in Terraform primarily do?

easy

A. Creates a new resource in the cloud

B. Transforms each item in a list or map into a new list or map

C. Deletes resources based on a condition

D. Runs a shell command on the local machine

Solution

1. Step 1: Understand the purpose of for expressions

   For expressions in Terraform are used to transform collections like lists or maps into new collections by applying a transformation to each item.

2. Step 2: Differentiate from other Terraform actions

   Creating or deleting resources and running shell commands are not done by for expressions; they are handled by resource blocks or provisioners.

3. Final Answer:

   Transforms each item in a list or map into a new list or map -> Option B

4. Quick Check:

   For expressions = transform collections [OK]

Hint: For expressions change each item in a list/map to a new form [OK]

Common Mistakes:

• Thinking for expressions create or delete resources
• Confusing for expressions with provisioners
• Assuming for expressions run commands

2. Which of the following is the correct syntax for a simple for expression transforming a list [1, 2, 3] to their squares in Terraform?

easy

A. [for n in [1, 2, 3] : n * n]

B. [for n : n * n in [1, 2, 3]]

C. [for n in [1, 2, 3] n * n]

D. [for n in [1, 2, 3] => n * n]

Solution

1. Step 1: Recall Terraform for expression syntax

   The correct syntax is: [for <variable> in <list> : <expression>]. [for n in [1, 2, 3] : n * n] matches this exactly.

2. Step 2: Check other options for syntax errors

   [for n : n * n in [1, 2, 3]] has wrong order, [for n in [1, 2, 3] n * n] misses colon, [for n in [1, 2, 3] => n * n] uses => which is invalid in Terraform for expressions.

3. Final Answer:

   [for n in [1, 2, 3] : n * n] -> Option A

4. Quick Check:

   Correct syntax = [for var in list : expr] [OK]

Hint: Remember syntax: for var in list : expression [OK]

Common Mistakes:

• Omitting the colon ':' after the list variable
• Using arrow '=>' instead of colon
• Placing expression before 'in' keyword

3. Given the Terraform expression:

[for s in ["apple", "banana", "cherry"] : upper(s) if length(s) > 5]

What is the resulting list?

medium

A. ["banana", "cherry"]

B. ["APPLE", "BANANA", "CHERRY"]

C. ["BANANA", "CHERRY"]

D. ["APPLE"]

Solution

1. Step 1: Identify filtering condition

   The expression filters strings with length greater than 5. "banana" (6) and "cherry" (6) qualify; "apple" (5) does not.

2. Step 2: Apply transformation function

   For qualifying strings, upper(s) converts them to uppercase: "BANANA", "CHERRY".

3. Final Answer:

   ["BANANA", "CHERRY"] -> Option C

4. Quick Check:

   Filter length > 5 + uppercase = ["BANANA", "CHERRY"] [OK]

Hint: Filter first, then transform inside for expression [OK]

Common Mistakes:

• Including items that don't meet the if condition
• Not applying the upper() function
• Confusing syntax order of filter and expression

4. Identify the error in this Terraform for expression:

[for k, v in {a=1, b=2} : "${k}=${v}" if v > 1]

medium

A. Using if condition outside the for expression

B. Missing colon after the map

C. Incorrect use of string interpolation syntax

D. Using two variables without parentheses in for expression

Solution

1. Step 1: Check syntax for multiple variables in for expressions

   When using two variables (key and value) in a for expression, parentheses are required: for (k, v) in map.

2. Step 2: Identify the error in given expression

   The expression uses 'for k, v in' without parentheses, causing syntax error.

3. Final Answer:

   Using two variables without parentheses in for expression -> Option D

4. Quick Check:

   Two variables need parentheses: for (k, v) in map [OK]

Hint: Use parentheses for multiple variables in for expressions [OK]

Common Mistakes:

• Omitting parentheses around multiple variables
• Placing if condition incorrectly
• Misusing string interpolation syntax

5. You have a map of instance names to their CPU counts:

{"web"=2, "db"=4, "cache"=1}

Write a Terraform for expression that creates a list of instance names with CPU count greater than 1, all in uppercase.

hard

A. [for (name, cpu) in {"web"=2, "db"=4, "cache"=1} : upper(name) if cpu > 1]

B. [for name, cpu in {"web"=2, "db"=4, "cache"=1} : upper(name) if cpu > 1]

C. [for (name, cpu) in {"web"=2, "db"=4, "cache"=1} : name if cpu > 1]

D. [for (name, cpu) in {"web"=2, "db"=4, "cache"=1} : upper(cpu) if cpu > 1]

Solution

1. Step 1: Use parentheses for key-value iteration

   When iterating over a map with two variables, use parentheses: for (name, cpu) in map.

2. Step 2: Apply filter and transformation

   Filter with if cpu > 1 to select "web" and "db". Transform name to uppercase with upper(name).

3. Final Answer:

   [for (name, cpu) in {"web"=2, "db"=4, "cache"=1} : upper(name) if cpu > 1] -> Option A

4. Quick Check:

   Parentheses + filter + upper(name) = [for (name, cpu) in {"web"=2, "db"=4, "cache"=1} : upper(name) if cpu > 1] [OK]

Hint: Parentheses for map keys, filter with if, transform with upper() [OK]

Common Mistakes:

• Omitting parentheses for key-value pairs
• Transforming cpu instead of name
• Not filtering correctly with if condition