How to create Preimage hash?

[Marware]

This is not clear in any related documentation

Sample code:

`call = substrate.compose_call(
call_module='Balances',
call_function='transfer',
call_params={
'dest': "5Gv8v85YeymUorg7No8vNAaaqpmSD71oT6RQYABnzEUXP9Af",
'value': 11111
})

hx = str(call).encode().hex() #1
storageFee = ((len(hx) - 2) / 2) * PreimageDepositConst
blake2_256(hx) #2`
Values of #1 and #2 (and storageFee) are different from what's generated on polkadot.js UI, and the results didn't work anyway

Any help or pointers would be appreciated
Thanks

[arjanz]

The way you used to determine the bytes of the call is not correct, the bytes of the call (and any ScaleType) are stored in the call.data attribute (this is of type ScaleBytes). So the actual bytes are stored in call.data.data. Also there is a convenience function that the string representation of a ScaleBytes is in 0x1234 hex-format, so you can also just use str(call.data)