[Tutor] Iterate through dictionary values and remove item

[GTXY20]

Hello all,

I have dictionary like the following:

d={(1,23A):[a,b,c,d],  (1,24A):[b,c,d], (2,23A):[a,b], (2,24A):[a,b,c,d]}

I would like to iterate through the dictionary such that if it finds
the value 'a' in the values of the key that it would remove the value
'b' from the values list. In addition if it finds 'a' in the values
list I would like it to take the first item from the key tuple k[0]
and and then look through the dictionary for that k[0] value and then
remove 'b' from its value list even if 'a' is not present in that
list. So at the end I would like my dictionary to end with:

d={(1,23A):[a,c,d],  (1,24A):[c,d], (2,23A):[a], (2,24A):[a,c,d]}

Initally I did the following:

for k,v in d.items():
u=k[0]
b=k[1]
if 'a' in v:
for k,v in d.items():
if k[0] == u:
for values in v:
if values == 'b':
v.remove(values)

However this will be a very big dictionary and it ended up running for
a very long time - in fact I had to kill the process.

Can anyone suggest an alternate method to do this?

Thanks in advance for any suggestions.

G.