Essential Books

Checking for allowed characters

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If you want to check that a string contains only a certain set of characters, in this case a-z, A-Z and 0-9, you can do so like this, 

import re

def is_allowed(string):
    characherRegex = re.compile(r'[^a-zA-Z0-9.]')
    string = characherRegex.search(string)
    return not bool(string)
    
print (is_allowed("abyzABYZ0099")) 
# Out: 'True'

print (is_allowed("#*@#$%^")) 
# Out: 'False'

You can also adapt the expression line from [^a-zA-Z0-9.] to [^a-z0-9.], to disallow uppercase letters for example.

Partial credit : http://stackoverflow.com/a/1325265/2697955

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Regular Expressions:
* Regular Expressions Regex
* Matching the beginning of a string
* Searching
* Precompiled patterns
* Flags
* Splitting a string using regular expressions
* Replacing
* Find All Non-Overlapping Matches
* Checking for allowed characters
* Grouping
* Escaping Special Characters
* Iterating over matches using re.finditer
* Match an expression only in specific locations
Table Of Contents
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189 Raise Custom Errors Exceptions
190 Using loops within functions
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