Multiline string substitution in Python

Question

I am trying this out:

account = "11111111111"
tenant_name= "Demo"
project_name= "demo"

sns_access_policy = """{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "0",
      "Effect": "Allow",
      "Principal": {
        "Service": "codestar-notifications.amazonaws.com"
      },
      "Action": "sns:Publish",
      "Resource": "arn:aws:sns:eu-west-1:{account_id}:{tenant_name}-{project_name}-pipeline-monitoring"
    }
  ]
}"""

sns_access_policy = sns_access_policy.replace("{account_id}",account).replace("{tenant_name}",tenant_name).replace("{project_name}",project_name)

This is doing my work, but I am looking for something like f{string_substitution}:

sns_access_policy = f"""{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "0",
      "Effect": "Allow",
      "Principal": {
        "Service": "codestar-notifications.amazonaws.com"
      },
      "Action": "sns:Publish",
      "Resource": "arn:aws:sns:eu-west-1:{account}:{tenant_name}-{project_name}-pipeline-monitoring"
    }
  ]
}"""

I am getting the following error:

SyntaxError: f-string: expressions nested too deeply

Is there any other way than using .replace() for this?

Asked By: Sumanth Shetty

||

Source

Answer 1

When you use an f-string all those braces start an expression, but in your case they are just literal braces. You have to use double braces for that.

sns_access_policy = f"""{{
  "Version": "2012-10-17",
  "Statement": [
    {{
      "Sid": "0",
      "Effect": "Allow",
      "Principal": {{
        "Service": "codestar-notifications.amazonaws.com"
      }},
      "Action": "sns:Publish",
      "Resource": "arn:aws:sns:eu-west-1:{account}:{tenant_name}-{project_name}-pipeline-monitoring"
    }}
  ]
}}"""

Answered By: Emanuel P

Multiline string substitution in Python

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