Add column to dataframe with constant value

Question

I have an existing dataframe which I need to add an additional column to which will contain the same value for every row   Existing df   Date  Open  High  Low  Close 01-01-2015  565  600  400  450   New df   Name  Date  Open  High  Low  Close abc  01-01-2015  565  600  400  450   I know how to append an existing series   dataframe column  But this is a different situation  because all I need is to add the  Name  column and set every row to the same value  in this case  abc

User · Answer

Summing up what the others have suggested  and adding a third way You can   assign   kwargs    df assign Name  abc     access the new column series  it will be created  and set it   df  Name      abc    insert loc  column  value  allow duplicates False   df insert 0   Name    abc      where the argument loc   0  lt   loc  lt   len columns    allows you to insert the column where you want   loc  gives you the index that your column will be at after the insertion  For example  the code above inserts the column Name as the 0-th column  i e  it will be inserted before the first column  becoming the new first column   Indexing starts from 0   All these methods allow you to add a new column from a Series as well  just substitute the  abc  default argument above with the series

User · Answer

Single liner works  df  Name      abc    Creates a Name column and sets all rows to abc value

User · Answer

df  Name    abc  will add the new column and set all rows to that value   In  79    df Out 79            Date  Open  High   Low   Close 0  01-01-2015   565   600   400     450 In  80    df  Name      abc  df Out 80            Date  Open  High   Low   Close Name 0  01-01-2015   565   600   400     450  abc

User · Answer

You can use insert to specify where you want to new column to be   In this case  I use 0 to place the new column at the left   df insert 0   Name    abc      Name        Date  Open  High  Low  Close 0  abc  01-01-2015   565   600  400    450

[python] Add column to dataframe with constant value

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