Ad-hoc analytics script to module/package
You may want to start by converting the process under __main__ into a function called main and then have it take command line arguments. That way, you separate user-configurable items from the actual program.

For example:

import re
import string
import sys
import os

import pandas as pd
from nltk.corpus import stopwords

def main(cmd_line_args):
  path_to_data_folder = cmd_line_args[1]
  os.chdir(path_to_data_folder)      

  # regular expression containing punctuation to be removed from strings
  regexp = re.compile('[%s]' % re.escape(''.join(p for p in   string.punctuation)))

  # set of stopwords to remove from text from NLTK
  stops = stopwords.words('english')

  # my data frame, containing only columns of text
  data_frame_filename =  cmd_line_args[2]
  df = pd.read_csv(data_frame_filename+".csv")

  # clean each column
  for col in df.columns.values:
      df[col] = clean_and_map_column(col, df, regexp)

  cleaned_filename = cmd_line_args[3]
  df.to_csv(cleaned_filename+".csv")


if __name__ == '__main__':
  main(sys.argv)