When creating a lambda to be used by another class I create one for each element in a list. This then gets called by other code, but the values used are only for the last value in the list.
I have a workaround but it's important to me to understand what's happening in the internals so I can avoid and write better Python going forward.
This code prints out '5' for each element in the array when I would expect it to print out the values 0 to 5. Why is it only using the last value?
markets = [0,1,2,3,4,5]
# Print outs 5, 5, 5, 5, 5
def not_working():
listeners = {
mkt: lambda bid, ask: f"{bid} {mkt}"
for mkt in markets}
return listeners
for key, listener in not_working().items():
print(listener(None, None))
This code prints correctly, but I don't really get why.
markets = [0,1,2,3,4,5]
# Prints out 1 2 3 4 5
make_lambda = lambda mkt: lambda bid, ask: mkt
def working():
listeners = {
mkt: make_lambda(mkt)
for mkt in markets}
return listeners
for key, listener in working().items():
print(listener(None, None))
