how do I convert a string to a valid variable name in python?

Question

I need to convert an arbitrary string to a string that is a valid variable name in python.

Here's a very basic example:

s1 = 'name/with/slashes' s2 = 'name '  def clean(s):     s = s.replace('/','')     s = s.strip()     return s  print clean(s1)+'_'#the _ is there so I can see the end of the string 

That is a very naive approach. I need to check if the string contains invalid variable name characters and replace them with ''

What would be a pythonic way to do this ?

Answer 1

Well, I'd like to best Triptych's solution with ... a one-liner!

>>> def clean(varStr): return re.sub('\W|^(?=\d)','_', varStr) ...  >>> clean('32v2 g #Gmw845h$W b53wi ') '_32v2_g__Gmw845h_W_b53wi_' 

This substitution replaces any non-variable appropriate character with underscore and inserts underscore in front if the string starts with a digit. IMO, 'name/with/slashes' looks better as variable name name_with_slashes than as namewithslashes.

Answer 2

According to Python, an identifier is a letter or underscore, followed by an unlimited string of letters, numbers, and underscores:

import re  def clean(s):     # Remove invalid characters    s = re.sub('[^0-9a-zA-Z_]', '', s)     # Remove leading characters until we find a letter or underscore    s = re.sub('^[^a-zA-Z_]+', '', s)     return s 

Use like this:

>>> clean(' 32v2 g #Gmw845h$W b53wi ') 'v2gGmw845hWb53wi'