可以使用for循环来迭代aws_iam_policy_document中principal中的identifiers。下面是代码示例：

# 导入依赖库
from pulumi_aws.iam import PolicyDocument

# 定义IAM策略文档
policy_doc = PolicyDocument(
    statement=[
        {
            "effect": "Allow",
            "action": ["s3:GetObject", "s3:PutObject"],
            "resource": ["arn:aws:s3:::my-bucket/*"],
            "principal": {
                "AWS": [
                    "arn:aws:iam::123456789012:user/user1",
                    "arn:aws:iam::123456789012:user/user2",
                    "arn:aws:iam::123456789012:role/role1",
                    "arn:aws:iam::123456789012:role/role2"
                ]
            }
        }
    ]
)

# 使用for循环迭代principal中的identifiers
for identifier in policy_doc.statement[0]['principal']['AWS']:
    print(identifier)