Merge Multiple feature classes based off name

Question

Trying to write a script to merge feature classes based off their name. Steps are as follows -

1. In the original geodatabase, find polygon feature classes that end with a particular suffix ( ie *15_AM)
2. In a new geodatabase, merge them together based on their names (So Peaks_15_AM, Peaks_14_AM and Peaks_13_AM to Peaks_AM)

I'm a novice and my code is very crude, it works for a single feature class but the loop does not accept a list for the 'Keyword' variable. I know I need to somehow iterate over a list but have been stuck how to approach it.

Ideally if I could use the feature class names without the suffix as the 'Keyword' that would be great, but could also just use some raw strings.

import arcpy
import os

#variables
arcpy.env.workspace = r"D:\Old.gdb"
OutputGDB = "D:\New.gdb"
FCS = set(arcpy.ListFeatureClasses("*15_AM", "polygon") + arcpy.ListFeatureClasses("*14_AM", "polygon") + arcpy.ListFeatureClasses("*13_AM", "polygon"))
Keyword = "Peaks"
fc = []

#merge
for i in FCS:
    if Keyword in i:
        fc.append(i)
        arcpy.Merge_management(fc,OutputGDB+"/"+Keyword+"_AM")

Answer 1

I recommend collections.defaultdict when grouping of some kind is involved:

import arcpy, os
from collections import defaultdict

arcpy.env.workspace = r'C:\scratch.gdb' #Change
output_gdb = r'C:\scratch2.gdb' #Change
lookfor = ['15_AM','14_AM'] #Change

d = defaultdict(list)
[d[l] for l in lookfor] #Add the keys

for feature in arcpy.ListFeatureClasses():
    for k,v in d.items(): #d.iteritems() py2/ArcMap
        if feature.endswith(k):
            d[k].append(feature)

#d is now:
#defaultdict(<class 'list'>, {'15_AM': ['ressers_15_AM', 'fhgg_15_AM'], '14_AM': ['sdfsdfs_14_AM', 'bvbnvbn_14_AM']})

for k,v in d.items():
    arcpy.Merge_management(inputs=v, output=os.path.join(output_gdb,'merged'+k))

Answer 2

Extending the @BERA's answer, I had to make some changes as I needed to merge based on the class (i.e. "ConservationArea") rather than the suffixes.

I've included a screenshot of the GDB, so you can see why I required startswith and endswith.

import arcpy, os
from collections import defaultdict

arcpy.env.workspace = r'D:\Data.gdb' #Change
output_gdb = r'D:\MASK_Merge_Combined_Test.gdb' #Change
lookfor = ['ConservationArea','Cape_Mtn'] #Change
Suffix = ('_15_AM','_14_AM','_13_AM')

d = defaultdict(list)
[d[l] for l in lookfor] #Add the keys

for feature in arcpy.ListFeatureClasses():
    for k,v in d.items(): #d.iteritems() py2/ArcMap
        if feature.startswith(k) and feature.endswith(Suffix):
            d[k].append(feature)

for k,v in d.items():
    arcpy.Merge_management(inputs=v, output=os.path.join(output_gdb,k+'_AM'))