Python多行字符串替换：f-string嵌套报错后的替代方案咨询

你遇到的f-string报错是因为JSON里的大括号和f-string语法冲突了——f-string会把JSON结构里的{当成变量占位符解析，导致嵌套层级超标。除了.replace()，还有这几种靠谱的多行字符串变量替换方法：

方法1：转义f-string中的JSON大括号 #

把JSON里的每个{改成{{，}}改成}}，让f-string只解析你真正需要替换的{account}这类变量占位符，不会误处理JSON结构的大括号：

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

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"
    }}
  ]
}}"""

优缺点：保留f-string的直观性，但模板复杂时手动转义容易漏改。

方法2：使用str.format()方法 #

直接复用你原来的模板字符串，调用format()传入变量即可，不需要处理转义，比多次.replace()更简洁：

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"
    }
  ]
}""".format(account_id=account, tenant_name=tenant_name, project_name=project_name)

优缺点：模板无需修改，代码整洁；如果占位符和变量名不一致，需要手动映射参数。

方法3：使用string.Template类 #

适合需要安全替换的场景（比如变量来自用户输入，避免格式字符串注入），用$作为占位符前缀：

from string import Template

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

template = Template("""{
  "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 = template.substitute(account_id=account, tenant_name=tenant_name, project_name=project_name)

优缺点：安全性高，不会解析模板中的特殊字符；但需要修改占位符格式为$前缀。

内容的提问来源于stack exchange，提问作者Sumanth Shetty