{"action":"created","issue":{"url":"https://api.github.com/repos/pydata/pandas/issues/9188","labels_url":"https://api.github.com/repos/pydata/pandas/issues/9188/labels{/name}","comments_url":"https://api.github.com/repos/pydata/pandas/issues/9188/comments","events_url":"https://api.github.com/repos/pydata/pandas/issues/9188/events","html_url":"https://github.com/pydata/pandas/issues/9188","id":53275265,"number":9188,"title":"BUG: concat of all-nan with empty frame produces object dtype","user":{"login":"jreback","id":953992,"avatar_url":"https://avatars.githubusercontent.com/u/953992?v=3","gravatar_id":"","url":"https://api.github.com/users/jreback","html_url":"https://github.com/jreback","followers_url":"https://api.github.com/users/jreback/followers","following_url":"https://api.github.com/users/jreback/following{/other_user}","gists_url":"https://api.github.com/users/jreback/gists{/gist_id}","starred_url":"https://api.github.com/users/jreback/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jreback/subscriptions","organizations_url":"https://api.github.com/users/jreback/orgs","repos_url":"https://api.github.com/users/jreback/repos","events_url":"https://api.github.com/users/jreback/events{/privacy}","received_events_url":"https://api.github.com/users/jreback/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/pydata/pandas/labels/Bug","name":"Bug","color":"e10c02"},{"url":"https://api.github.com/repos/pydata/pandas/labels/Dtypes","name":"Dtypes","color":"e102d8"},{"url":"https://api.github.com/repos/pydata/pandas/labels/Reshaping","name":"Reshaping","color":"02d7e1"}],"state":"open","locked":false,"assignee":null,"milestone":{"url":"https://api.github.com/repos/pydata/pandas/milestones/25","labels_url":"https://api.github.com/repos/pydata/pandas/milestones/25/labels","id":569113,"number":25,"title":"0.16.0","description":"after 0.15 of course!","creator":{"login":"jreback","id":953992,"avatar_url":"https://avatars.githubusercontent.com/u/953992?v=3","gravatar_id":"","url":"https://api.github.com/users/jreback","html_url":"https://github.com/jreback","followers_url":"https://api.github.com/users/jreback/followers","following_url":"https://api.github.com/users/jreback/following{/other_user}","gists_url":"https://api.github.com/users/jreback/gists{/gist_id}","starred_url":"https://api.github.com/users/jreback/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jreback/subscriptions","organizations_url":"https://api.github.com/users/jreback/orgs","repos_url":"https://api.github.com/users/jreback/repos","events_url":"https://api.github.com/users/jreback/events{/privacy}","received_events_url":"https://api.github.com/users/jreback/received_events","type":"User","site_admin":false},"open_issues":880,"closed_issues":190,"state":"open","created_at":"2014-02-14T03:31:22Z","updated_at":"2015-01-20T20:03:54Z","due_on":"2015-02-28T08:00:00Z","closed_at":null},"comments":1,"created_at":"2015-01-02T20:20:20Z","updated_at":"2015-01-21T05:36:39Z","closed_at":null,"body":"xref #9149\r\n\r\nThe resultant has all missing and when concat with an empty frame should result in the same dtype (and not promotion)\r\n\r\n```\r\nIn [1]: df_1 = pd.DataFrame({\"Row\":[0,1,1], \"EmptyCol\":np.nan, \"NumberCol\":[1,2,3]})\r\n\r\nIn [2]: df_2 = pd.DataFrame(columns = df_1.columns)\r\n\r\nIn [3]: df_concat = pd.concat([df_1, df_2], axis=0)\r\n\r\nIn [4]: df_1.dtypes\r\nOut[4]: \r\nEmptyCol     float64\r\nNumberCol      int64\r\nRow            int64\r\ndtype: object\r\n\r\nIn [6]: df_2.dtypes\r\nOut[6]: \r\nEmptyCol     object\r\nNumberCol    object\r\nRow          object\r\ndtype: object\r\n\r\nIn [7]: df_concat.dtypes\r\nOut[7]: \r\nEmptyCol      object\r\nNumberCol    float64\r\nRow          float64\r\ndtype: object\r\n```"},"comment":{"url":"https://api.github.com/repos/pydata/pandas/issues/comments/70787162","html_url":"https://github.com/pydata/pandas/issues/9188#issuecomment-70787162","issue_url":"https://api.github.com/repos/pydata/pandas/issues/9188","id":70787162,"user":{"login":"tvyomkesh","id":911431,"avatar_url":"https://avatars.githubusercontent.com/u/911431?v=3","gravatar_id":"","url":"https://api.github.com/users/tvyomkesh","html_url":"https://github.com/tvyomkesh","followers_url":"https://api.github.com/users/tvyomkesh/followers","following_url":"https://api.github.com/users/tvyomkesh/following{/other_user}","gists_url":"https://api.github.com/users/tvyomkesh/gists{/gist_id}","starred_url":"https://api.github.com/users/tvyomkesh/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/tvyomkesh/subscriptions","organizations_url":"https://api.github.com/users/tvyomkesh/orgs","repos_url":"https://api.github.com/users/tvyomkesh/repos","events_url":"https://api.github.com/users/tvyomkesh/events{/privacy}","received_events_url":"https://api.github.com/users/tvyomkesh/received_events","type":"User","site_admin":false},"created_at":"2015-01-21T05:36:39Z","updated_at":"2015-01-21T05:36:39Z","body":"Have submitted a first cut PR (https://github.com/pydata/pandas/pull/9303) for this one. One test fails due to changed behavior. Looking for some discussion, comments and inputs. If I am not totally misplaced, I would love to take this up and work on the PR. Thanks all for your time and inputs. Much valuable for newbies :-)."}}