迁移失败！试试这个脚本删除 Django 项目下的迁移文件

当你在终端上输入如下的命令执行数据迁移的时候：

python manage.py makemigrations
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它报错了！

/usr/lib/python3/dist-packages/requests/__init__.py:80: RequestsDependencyWarning: urllib3 (1.26.4) or chardet (3.0.4) doesn't match a supported version!
  RequestsDependencyWarning)
Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 85, in wrapped
    res = handle_func(*args, **kwargs)
  File "/usr/local/lib/python3.6/dist-packages/django/core/management/commands/makemigrations.py", line 87, in handle
    loader = MigrationLoader(None, ignore_no_migrations=True)
  File "/usr/local/lib/python3.6/dist-packages/django/db/migrations/loader.py", line 53, in __init__
    self.build_graph()
  File "/usr/local/lib/python3.6/dist-packages/django/db/migrations/loader.py", line 255, in build_graph
    self.graph.validate_consistency()
  File "/usr/local/lib/python3.6/dist-packages/django/db/migrations/graph.py", line 195, in validate_consistency
    [n.raise_error() for n in self.node_map.values() if isinstance(n, DummyNode)]
  File "/usr/local/lib/python3.6/dist-packages/django/db/migrations/graph.py", line 195, in <listcomp>
    [n.raise_error() for n in self.node_map.values() if isinstance(n, DummyNode)]
  File "/usr/local/lib/python3.6/dist-packages/django/db/migrations/graph.py", line 58, in raise_error
    raise NodeNotFoundError(self.error_message, self.key, origin=self.origin)
django.db.migrations.exceptions.NodeNotFoundError: Migration comments.0001_initial dependencies reference nonexistent parent node ('tweets', '0002_auto_20210426_0742')

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面对红红的一堆的错误，怒火中烧，而 Django 又没有提供删除迁移文件的命令 ? ，而手动删除又非常的无趣和浪费时间！
我提供了一个 Python 写的脚本，来删除迁移文件，放到你项目的根目录并执行它吧！

import os

for root, dirs, files in os.walk('.'):
    if 'migrations' in dirs:
        dir = dirs[dirs.index('migrations')]
        for root_j, dirs_j, files_j in os.walk(os.path.join(root, dir)):
            for file_k in files_j:
                if file_k != '__init__.py':
                    dst_file = os.path.join(root_j, file_k)
                    print('>>> ', dst_file)
                    os.remove(dst_file)

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整体的思路就是，先通过 os.walk 递归遍历项目根路径下所有的文件夹，找到所有名为 migrations 文件夹，除了 __init__.py 文件，删除里面所有的文件。为什么不能删除 __init__.py 文件呢？因为没有 __init__.py 文件就不是一个 Python 包了，执行迁移命令的时候就不会迁移这个 app 下的 Models

这里在提供一种思路，就是先找到所有的 migrations 文件夹，然后删除它们，在原位置重新创建，记得在文件夹里面创建一个名为 __init__.py 的空文件哦！

为什么要选 Python 脚本来做这件事情呢？当然是 Python 的跨平台特性，这样不管是 UNIX 还是 Windows 都可以使用。

当然上面这段代码非常的丑陋 ? ，谁有空可以优化一下后再发我一段吧！