You’ve now seen how to use loops to create multiple copies of entire resources and inline blocks, but what if you need a loop to set a single variable or parameter?

Imagine that you wrote some Terraform code that took in a list of names:

variable "names" {

description = "A list of names"

type = list(string)

default = ["neo", "trinity", "morpheus"]

}

How could you convert all of these names to uppercase? In a general-purpose programming language such as Python, you could write the following for-loop:

names = ["neo", "trinity", "morpheus"]

upper_case_names = []

for name in names:

upper_case_names.append(name.upper())

print upper_case_names

Python offers another way to write the exact for-loop in one line using a syntax known as a list comprehension:

upper_case_names = [name.upper() for name in names]

Python also allows you to filter the resulting list by specifying a condition:

short_upper_case_names = [name.upper() for name in names if len(name) < 5]

Terraform offers similar functionality in the form of a for expression (not to be confused with the for_each expression you saw in the previous section). The basic syntax of a for expression is as follows:

[for in :

]