验证数字和字母

Question

There have been cases where I have needed to validate a string filled with numbers and letters and I want to know the easiest way to do it

For example, in Tic Tac Toe / Noughts and Crosses, I need to make sure that the position that the user has entered is between "1-3" and "ac"

For better understanding of what I am asking:

pos = "2c"
>>> Input is valid

pos = "1z"
>>> Input is invalid: Letters outside range a-c

pos = "5b"
>>> Input is invalid: Numbers outside range 1-3

Answer 1

There are only 9 possible valid inputs, so you could just check them all, or you could use a regular expression to see if the input matches all the valid inputs.

import re

pattern = re.compile(r'^[123][abc]$')
m = pattern.match("2b")
if m:
    print("It's a match!")

The regular expression r'^[123][abc]$' looks for the start of a string, followed by 1, 2, or 3, followed by a, b, or c, followed by the end of the string. No inputs outside that range (or that are longer than two characters) should match.

Answer 2

Without regular expressions, you could have something like:

def validate(i):
    if type(i) != str or len(i) != 2:
        return False
    d, char = int(i[0]), i[1]
    return d >= 1 and d <= 3 and char in 'abc'

print(validate('1c')) #True
print(validate('3a')) #True
print(validate('2b')) #True

print(validate('36')) # False
print(validate('106')) # False
print(validate('10c')) # False
print(validate(10)) # False

This does, however, assume that the first character in your input can be converted to an int .

Answer 3

Use regex as follows:

import re

example_str = '1c'
p = re.compile('^[1-3][a-c]$')

if p.match(example_str):
  # Valid
else:
  # Invalid

You can use - for range selection in pattern.