Getting syntax warning: `invalid escape sequence '\D'`

[corneliusroemer]

Not quite sure why, but i'm getting the following syntax warning from functions.py:

/Users/corneliusromer/code/chronic_infection_python/covid_mutation_distribution/functions.py:143: SyntaxWarning: invalid escape sequence '\D'
  int_nuc_list = [re.sub('\D', '', i) for i in mutated_nucleotide_list]
/Users/corneliusromer/code/chronic_infection_python/covid_mutation_distribution/functions.py:149: SyntaxWarning: invalid escape sequence '\D'
  int_nuc_list = [re.sub('\D', '', i) for i in mutated_nucleotide_list]
/Users/corneliusromer/code/chronic_infection_python/covid_mutation_distribution/functions.py:304: SyntaxWarning: invalid escape sequence '\d'
  nuc_pos_list_no_digits = [re.sub('\d+', '', i) for i in nuc_list_upper]
/Users/corneliusromer/code/chronic_infection_python/covid_mutation_distribution/functions.py:356: SyntaxWarning: invalid escape sequence '\D'
  int_nuc_list = [re.sub('\D', '', i) for i in nuc_pos_list_parsed]