TypeError：只能将列表（不是“str”）连接到列表 |蒸馏器迁移答案

【问题标题】：TypeError: can only concatenate list (not "str") to list | Alembic MigrationTypeError：只能将列表（不是“str”）连接到列表 |蒸馏器迁移
【发布时间】：2020-06-02 23:05:19
【问题描述】：

我正在尝试运行迁移以添加外键约束。这是当我尝试在多对一关系中将artist_id 添加到我的RSVP 模型时。每个RSVP只能有一个艺术家，一个艺术家可以有多个rsvps。

这是我的迁移代码

def upgrade():
    with op.batch_alter_table('rsvp') as batch_op:
        batch_op.create_foreign_key(
            "fk_artist_rsvp", "rsvp",
            "artist", ["artist_id"], ["id"])

def downgrade():
    with op.batch_alter_table('rsvp') as batch_op:
        batch_op.drop_constraint(
            u'fk_artist_rsvp', 'artist', type_='foreignkey')

当我运行它时，我得到以下错误

    Traceback (most recent call last):
  File "/Users/dariusmandres/.pyenv/versions/st-art/bin/alembic", line 11, in <module>
    load_entry_point('alembic==1.4.0', 'console_scripts', 'alembic')()
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/config.py", line 577, in main
    CommandLine(prog=prog).main(argv=argv)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/config.py", line 571, in main
    self.run_cmd(cfg, options)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/config.py", line 551, in run_cmd
    **dict((k, getattr(options, k, None)) for k in kwarg)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/command.py", line 298, in upgrade
    script.run_env()
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/script/base.py", line 489, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
    module = load_module_py(module_id, path)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/util/compat.py", line 173, in load_module_py
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "alembic/env.py", line 77, in <module>
    run_migrations_online()
  File "alembic/env.py", line 71, in run_migrations_online
    context.run_migrations()
  File "<string>", line 8, in run_migrations
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/runtime/environment.py", line 846, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/runtime/migration.py", line 518, in run_migrations
    step.migration_fn(**kw)
  File "/Users/dariusmandres/projects/st-art/alembic/versions/1d80258c8056_artist_rsvp.py", line 23, in upgrade
    "artist", ["artist_id"], ["id"])
  File "<string>", line 3, in create_foreign_key
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/operations/ops.py", line 702, in batch_create_foreign_key
    return operations.invoke(op)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/operations/base.py", line 374, in invoke
    return fn(self, operation)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/operations/toimpl.py", line 151, in create_constraint
    operation.to_constraint(operations.migration_context)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/operations/ops.py", line 547, in to_constraint
    **self.kw
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/alembic/operations/schemaobj.py", line 46, in foreign_key_constraint
    schema=referent_schema
  File "<string>", line 2, in __new__
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/sqlalchemy/util/deprecations.py", line 130, in warned
    return fn(*args, **kwargs)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/sqlalchemy/sql/schema.py", line 470, in __new__
    key = _get_table_key(name, schema)
  File "/Users/dariusmandres/.pyenv/versions/3.7.0/envs/st-art/lib/python3.7/site-packages/sqlalchemy/sql/schema.py", line 77, in _get_table_key
    return schema + "." + name
TypeError: can only concatenate list (not "str") to list

发生了什么事？

【问题讨论】：

您能否发布更多的堆栈跟踪信息，以便我们轻松找出您的代码的哪一行有问题？
@tdelaney 添加了完整的堆栈跟踪。
您在运行flask db upgrade 命令时是否收到此错误？并且您手动修改了migrations.py 文件吗？
@Ejaz 我正在使用alembic upgrade head 并收到此错误。我没有migrations.py 文件。

标签： python sqlalchemy flask-sqlalchemy alembic flask-migrate

【解决方案1】：

问题源于op.create_foreign_key和batch_op.create_foreign_key之间的语法不同...

    def upgrade():
        with op.batch_alter_table('rsvp') as batch_op:
            batch_op.create_foreign_key(
                "fk_artist_rsvp", "rsvp",
                "artist", ["artist_id"], ["id"])

应该是：

    def upgrade():
        with op.batch_alter_table('rsvp') as batch_op:
            batch_op.create_foreign_key(
                "fk_artist_rsvp",
                "artist", ["artist_id"], ["id"])

（不需要在批处理操作中提供表名）

【讨论】：