In pyspark, how do you add/concat a string to a column?

Question

I would like to add a string to an existing column. For example, df[\'col1\'] has values as \'1\', \'2\', \'3\' etc and I would like to concat stri

Answer 1

Another option here is to use pyspark.sql.functions.format_string() which allows you to use C printf style formatting.

Here's an example where the values in the column are integers.

import pyspark.sql.functions as f
df = sqlCtx.createDataFrame([(1,), (2,), (3,), (10,), (100,)], ["col1"])
df.withColumn("col2", f.format_string("%03d", "col1")).show()
#+----+----+
#|col1|col2|
#+----+----+
#|   1| 001|
#|   2| 002|
#|   3| 003|
#|  10| 010|
#| 100| 100|
#+----+----+

Here the format "%03d" means print an integer number left padded with up to 3 zeros. This is why the 10 gets mapped to 010 and 100 does not change at all.

Or if you wanted to add exactly 3 zeros in the front:

df.withColumn("col2", f.format_string("000%d", "col1")).show()
#+----+------+
#|col1|  col2|
#+----+------+
#|   1|  0001|
#|   2|  0002|
#|   3|  0003|
#|  10| 00010|
#| 100|000100|
#+----+------+