{"action":"created","issue":{"url":"https://api.github.com/repos/pydata/pandas/issues/9239","labels_url":"https://api.github.com/repos/pydata/pandas/issues/9239/labels{/name}","comments_url":"https://api.github.com/repos/pydata/pandas/issues/9239/comments","events_url":"https://api.github.com/repos/pydata/pandas/issues/9239/events","html_url":"https://github.com/pydata/pandas/pull/9239","id":54193793,"number":9239,"title":"API: Add DataFrame.assign method","user":{"login":"TomAugspurger","id":1312546,"avatar_url":"https://avatars.githubusercontent.com/u/1312546?v=3","gravatar_id":"","url":"https://api.github.com/users/TomAugspurger","html_url":"https://github.com/TomAugspurger","followers_url":"https://api.github.com/users/TomAugspurger/followers","following_url":"https://api.github.com/users/TomAugspurger/following{/other_user}","gists_url":"https://api.github.com/users/TomAugspurger/gists{/gist_id}","starred_url":"https://api.github.com/users/TomAugspurger/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/TomAugspurger/subscriptions","organizations_url":"https://api.github.com/users/TomAugspurger/orgs","repos_url":"https://api.github.com/users/TomAugspurger/repos","events_url":"https://api.github.com/users/TomAugspurger/events{/privacy}","received_events_url":"https://api.github.com/users/TomAugspurger/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/pydata/pandas/labels/API%20Design","name":"API Design","color":"AD7FA8"}],"state":"closed","locked":false,"assignee":null,"milestone":{"url":"https://api.github.com/repos/pydata/pandas/milestones/25","html_url":"https://github.com/pydata/pandas/milestones/0.16.0","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":808,"closed_issues":303,"state":"open","created_at":"2014-02-14T03:31:22Z","updated_at":"2015-03-01T14:51:09Z","due_on":"2015-03-10T04:00:00Z","closed_at":null},"comments":53,"created_at":"2015-01-13T13:32:24Z","updated_at":"2015-03-01T17:54:47Z","closed_at":"2015-03-01T14:51:09Z","pull_request":{"url":"https://api.github.com/repos/pydata/pandas/pulls/9239","html_url":"https://github.com/pydata/pandas/pull/9239","diff_url":"https://github.com/pydata/pandas/pull/9239.diff","patch_url":"https://github.com/pydata/pandas/pull/9239.patch"},"body":"Closes https://github.com/pydata/pandas/issues/9229\r\n\r\nsignature: `DataFrame.transform(**kwargs)`\r\n\r\n- the keyword is the name of the new column (existing columns are overwritten if there's a name conflict, as in dplyr)\r\n- the value is either\r\n  - called on self if it's callable. The callable should be a function of 1 argument, the DataFrame being called on.\r\n  - inserted otherwise\r\n\r\n\r\n```python\r\nIn [7]: df.head()\r\nOut[7]: \r\n   sepal_length  sepal_width  petal_length  petal_width species\r\n0           5.1          3.5           1.4          0.2  setosa\r\n1           4.9          3.0           1.4          0.2  setosa\r\n2           4.7          3.2           1.3          0.2  setosa\r\n3           4.6          3.1           1.5          0.2  setosa\r\n4           5.0          3.6           1.4          0.2  setosa\r\n\r\nIn [8]: (df.query('species == \"virginica\"')\r\n           .transform(sepal_ratio=lambda x: x.sepal_length / x.sepal_width)\r\n           .head())\r\nOut[8]: \r\n     sepal_length  sepal_width  petal_length  petal_width    species  \\\r\n100           6.3          3.3           6.0          2.5  virginica   \r\n101           5.8          2.7           5.1          1.9  virginica   \r\n102           7.1          3.0           5.9          2.1  virginica   \r\n103           6.3          2.9           5.6          1.8  virginica   \r\n104           6.5          3.0           5.8          2.2  virginica   \r\n\r\n     sepal_ratio  \r\n100     1.909091  \r\n101     2.148148  \r\n102     2.366667  \r\n103     2.172414  \r\n104     2.166667  \r\n```\r\n\r\nMy question now is\r\n\r\n- How strict should we be on the shape of the `transformed` DataFrame? Should we do any kind of checking on the index or columns?\r\n"},"comment":{"url":"https://api.github.com/repos/pydata/pandas/issues/comments/76620807","html_url":"https://github.com/pydata/pandas/pull/9239#issuecomment-76620807","issue_url":"https://api.github.com/repos/pydata/pandas/issues/9239","id":76620807,"user":{"login":"shoyer","id":1217238,"avatar_url":"https://avatars.githubusercontent.com/u/1217238?v=3","gravatar_id":"","url":"https://api.github.com/users/shoyer","html_url":"https://github.com/shoyer","followers_url":"https://api.github.com/users/shoyer/followers","following_url":"https://api.github.com/users/shoyer/following{/other_user}","gists_url":"https://api.github.com/users/shoyer/gists{/gist_id}","starred_url":"https://api.github.com/users/shoyer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/shoyer/subscriptions","organizations_url":"https://api.github.com/users/shoyer/orgs","repos_url":"https://api.github.com/users/shoyer/repos","events_url":"https://api.github.com/users/shoyer/events{/privacy}","received_events_url":"https://api.github.com/users/shoyer/received_events","type":"User","site_admin":false},"created_at":"2015-03-01T17:54:47Z","updated_at":"2015-03-01T17:54:47Z","body":"Woohoo! Well done :+1:"}}