How to loop through python dictionary keys using wild cards? - wildcard

Question

I have created a dictionary and am looping through it to create a final, much smaller dictionary. I have successfully done this, but it is long and cumbersome. It seems to me I should be able to loop through using some sort of wildcard. My problem is that I am using user input, but some keys can be a, a_1, a_2, ...a_5. Not all go up to 5 possible options, and some have as few as one. Please be kind, I am new to programming. I have tried the fnmatch() function to no avail.
check_parm=yae_list.values()
new_dict={}
x=int(len(check_parm))
while x>0:
element=check_parm[x-1]
if element in yae_atom_parms_dic:
new_dict[element]=yae_atom_parms_dic.get(element)
elif not yae_atom_parms_dic.get(element):
element_1=element+'_1'
if element_1 in yae_atom_parms_dic:
new_dict[element_1]=yae_atom_parms_dic.get(element_1)
element_2=element+'_2'
if element_2 in yae_atom_parms_dic:
new_dict[element_2]=yae_atom_parms_dic.get(element_2)
element_3=element+'_3'
if element_3 in yae_atom_parms_dic:
new_dict[element_3]=yae_atom_parms_dic.get(element_3)
element_4=element+'_4'
if element_4 in yae_atom_parms_dic:
new_dict[element_4]=yae_atom_parms_dic.get(element_4)
element_5=element+'_5'
if element_5 in yae_atom_parms_dic:
new_dict[element_5]=yae_atom_parms_dic.get(element_5)
if element_1 or element_2 or element_3 or element_4 or element_5:
print("Which one do you want?")
print new_dict
x=x-1
This is working as I would like, giving the output:
Which one do you want?
{'C_1': (6, 4, 1, 2, 's', -21.4, 1.625, 0, 1, 0), 'C_2': (6, 4, 1, 2, 'p', -11.4,1.625,)}

Answer 1

Can try something like this:
import re
constant_keys = "|".join(map(re.escape, yae_list.values()))
re_expression = re.compile("^(%s)(_[1-5])?$" % constant_keys)
allowed_keys = filter(re_expression.match, yea_atom_parms_dic.keys())
new_dict = {key: yea_atom_parms_dic[key] for key in allowed_keys}
print new_dict
In this one, first you construct regular expression by joining all of the yae_list keys by | character (and escaping them) and then you put such an expression into ^(%s)(_[1-5])? which means that the match would be hit when the key is either equal to any of the keys in | sequence optionally suffixed with underscore and the number between 1 and 5. Next you filter the allowed keys and using them you can create the new dict with the keys from allowed_keys list.
Example:
If you have the keys: "C", "a" and "new", then the regular expression would looks as follow: ^(C|a|new)(_[1-5])?$