<human>:  how to count the number of letters in uing len.
<bot>: Here is a Python function to count the number of letters in a sentence

import string

def count_letters(string):
  """
  Count the number of letters in a string.
  """
  return len(string)

# Enter the string
string = 'hello'

# Calling the function
print((count_letters(string)))

#Example Output
# 5

#Remember to inspect code for bugs.