{"action":"created","comment":{"url":"https://api.github.com/repos/pydata/pandas/pulls/comments/37100001","id":37100001,"diff_hunk":"@@ -2552,6 +2552,22 @@ def _constructor(self):\n \n         tm.assertIsInstance(result, NotADataFrame)\n \n+    def test_empty_sequence_concat(self):\n+        empty_pat = \"[Nn]o 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the issue number here as a comment","created_at":"2015-08-14T17:41:17Z","updated_at":"2015-08-14T17:41:17Z","html_url":"https://github.com/pydata/pandas/pull/9172#discussion_r37100001","pull_request_url":"https://api.github.com/repos/pydata/pandas/pulls/9172","_links":{"self":{"href":"https://api.github.com/repos/pydata/pandas/pulls/comments/37100001"},"html":{"href":"https://github.com/pydata/pandas/pull/9172#discussion_r37100001"},"pull_request":{"href":"https://api.github.com/repos/pydata/pandas/pulls/9172"}}},"pull_request":{"url":"https://api.github.com/repos/pydata/pandas/pulls/9172","id":26685514,"html_url":"https://github.com/pydata/pandas/pull/9172","diff_url":"https://github.com/pydata/pandas/pull/9172.diff","patch_url":"https://github.com/pydata/pandas/pull/9172.patch","issue_url":"https://api.github.com/repos/pydata/pandas/issues/9172","number":9172,"state":"open","locked":false,"title":"ERR: better concat error messages #9157","user":{"login":"cel4","id":3819470,"avatar_url":"https://avatars.githubusercontent.com/u/3819470?v=3","gravatar_id":"","url":"https://api.github.com/users/cel4","html_url":"https://github.com/cel4","followers_url":"https://api.github.com/users/cel4/followers","following_url":"https://api.github.com/users/cel4/following{/other_user}","gists_url":"https://api.github.com/users/cel4/gists{/gist_id}","starred_url":"https://api.github.com/users/cel4/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/cel4/subscriptions","organizations_url":"https://api.github.com/users/cel4/orgs","repos_url":"https://api.github.com/users/cel4/repos","events_url":"https://api.github.com/users/cel4/events{/privacy}","received_events_url":"https://api.github.com/users/cel4/received_events","type":"User","site_admin":false},"body":"closes #9157 \r\n\r\nThis is a first attempt to improve the error message when trying to concat an empty list/set of objects:\r\n\r\n`pd.concat([])` currently raises following error:\r\n\r\n```\r\n/Users/ch/miniconda/envs/sci33/lib/python3.3/site-packages/pandas/tools/merge.py in __init__(self, objs, axis, join, join_axes, keys, levels, names, ignore_index, verify_integrity, copy)\r\n    765 \r\n    766         if len(objs) == 0:\r\n--> 767             raise ValueError('All objects passed were None')\r\n    768 \r\n    769         # consolidate data & figure out what our result ndim is going to be\r\n\r\nValueError: All objects passed were None\r\n```\r\n\r\nAfter the tiny fix it is:\r\n```\r\n/Users/ch/repo/pandas/pandas/tools/merge.py in __init__(self, objs, axis, join, join_axes, keys, levels, names, ignore_index, verify_integrity, copy)\r\n    767 \r\n    768         if len(objs) == 0:\r\n--> 769             raise ValueError('No objects passed')\r\n    770 \r\n    771         if isinstance(objs, dict):\r\n\r\nValueError: No objects passed\r\n```\r\n","created_at":"2014-12-30T13:35:46Z","updated_at":"2015-08-14T17:41:17Z","closed_at":null,"merged_at":null,"merge_commit_sha":"94ae2a6206615703546430652d8a7c854dd4d31e","assignee":null,"milestone":null,"commits_url":"https://api.github.com/repos/pydata/pandas/pulls/9172/commits","review_comments_url":"https://api.github.com/repos/pydata/pandas/pulls/9172/comments","review_comment_url":"https://api.github.com/repos/pydata/pandas/pulls/comments{/number}","comments_url":"https://api.github.com/repos/pydata/pandas/issues/9172/comments","statuses_url":"https://api.github.com/repos/pydata/pandas/statuses/a2c54e5bb69bf9f1052cc36aec03a5e913804b9b","head":{"label":"cel4:concat_error","ref":"concat_error","sha":"a2c54e5bb69bf9f1052cc36aec03a5e913804b9b","user":{"login":"cel4","id":3819470,"avatar_url":"https://avatars.githubusercontent.com/u/3819470?v=3","gravatar_id":"","url":"https://api.github.com/users/cel4","html_url":"https://github.com/cel4","followers_url":"https://api.github.com/users/cel4/followers","following_url":"https://api.github.com/users/cel4/following{/other_user}","gists_url":"https://api.github.com/users/cel4/gists{/gist_id}","starred_url":"https://api.github.com/users/cel4/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/cel4/subscriptions","organizations_url":"https://api.github.com/users/cel4/orgs","repos_url":"https://api.github.com/users/cel4/repos","events_url":"https://api.github.com/users/cel4/events{/privacy}","received_events_url":"https://api.github.com/users/cel4/received_events","type":"User","site_admin":false},"repo":{"id":28630733,"name":"pandas","full_name":"cel4/pandas","owner":{"login":"cel4","id":3819470,"avatar_url":"https://avatars.githubusercontent.com/u/3819470?v=3","gravatar_id":"","url":"https://api.github.com/users/cel4","html_url":"https://github.com/cel4","followers_url":"https://api.github.com/users/cel4/followers","following_url":"https://api.github.com/users/cel4/following{/other_user}","gists_url":"https://api.github.com/users/cel4/gists{/gist_id}","starred_url":"https://api.github.com/users/cel4/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/cel4/subscriptions","organizations_url":"https://api.github.com/users/cel4/orgs","repos_url":"https://api.github.com/users/cel4/repos","events_url":"https://api.github.com/users/cel4/events{/privacy}","received_events_url":"https://api.github.com/users/cel4/received_events","type":"User","site_admin":false},"private":false,"html_url":"https://github.com/cel4/pandas","description":"Flexible 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