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valid_passwords2

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Write a function named valid_passwords2 (similar to the previous exercise valid_passwords) that examines a list of passwords and password policies and returns how many of the passwords are acceptable by those policies. Your function accepts a string parameter representing a file name as a parameter. Each line of the file contains a policy followed by a password. A policy is of the form INDEX1-INDEX2 LETTER indicating that the given letter must occur at exactly one of the two given 1-based indexes in the password. For example, if the file named passwords.txt contains the following values: 

1-3 a: abcde
1-3 b: cdefg
2-9 c: ccccccccc

The first line, abcde is valid: position 1 contains a and position 3 does not. The second line, cdefg is invalid: neither position 1 nor position 3 contains b. The third line, ccccccccc is invalid: both position 2 and position 9 contain c. So the call of valid_passwords2("passwords.txt") should return 1. Note again that the indexes given are 1-based, not 0-based.

You may assume that the file exists and is readable and that it follows the format described above.

Function: Write a Python function as described, not a complete program.

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