Check if string only contains characters from list of characters/symbols?

Question

How can I check in Python 3 that a string contains only characters/symbols from a given list?

Given:

• a list allowedSymbols = [\'b\', \'c\', \'z\', \'

Answer 1

The more Pythonic way is to use all(), it's faster, shorter, clearer and you don't need a loop:

allowedSymbols = ['b', 'c', 'z', ':']

enteredpass1 = 'b:c::z:bc:'
enteredpass2 = 'bc:y:z'

# We can use a list-comprehension... then apply all() to it...
>>> [c in allowedSymbols for c in enteredpass1]
[True, True, True, True, True, True, True, True, True, True]

>>> all(c in allowedSymbols for c in enteredpass1)
True
>>> all(c in allowedSymbols for c in enteredpass2)
False

Also note there's no gain in allowedSymbols being a list of chars instead of a simple string: allowedSymbols = 'bcz:' (The latter is more compact in memory and probably tests faster too)

But you can easily convert the list to a string with ''.join(allowedSymbols)

>>> allowedSymbols_string = 'bcz:'

>>> all(c in allowedSymbols_string for c in enteredpass1)
True
>>> all(c in allowedSymbols_string for c in enteredpass2)
False

Please see the doc for the helpful builtins any() and all(), together with list comprehensions or generator expressions they are very powerful.