chained-assignment

The SettingWithCopyWarning was created to flag potentially confusing “chained” assignments, such as the following, which does not always work as expected, particularly when the first selection returns a copy. [see GH5390 and GH5597 for background discussion.] df[df[‘A’] > 2][‘B’] = new_val # new_val not set in df The warning offers a suggestion to rewrite as … Read more

Edit 2017 As indicated in the comments and by @Alexander, currently the best method to add the values of a Series as a new column of a DataFrame could be using assign: df1 = df1.assign(e=pd.Series(np.random.randn(sLength)).values) Edit 2015 Some reported getting the SettingWithCopyWarning with this code. However, the code still runs perfectly with the current pandas … Read more