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Python isalnum String ExampleUse the isalnum method to see whether a string contains only letters and digits.
Isalnum. Sometimes we want to ensure a Python string has no punctuation or other whitespace. We can see if it contains just letters and digits.
With isalnum, we have a method that loops over the characters in the string. If any whitespace, punctuation, or other characters are found, it returns false.
string.punctuation
An example. Here we see a program that uses isalnum. We can call isalnum() on a string instance, or use str.isanum and pass the string as the argument.
Tests We have 7 strings in our tests list. Some have spaces, punctuation, and one is an empty string.
Result The only strings that cause isalnum to return true are the ones with no whitespace or punctuation (and at least 1 character).
Python program that uses isalnum method
tests = [] tests.append("Dot Net Perls") tests.append("DotNetPerls") tests.append("Dot_Net_Perls") tests.append("Dot0123") tests.append("dotnetperls") tests.append("123") tests.append("") for test in tests: # Test each string for alphanumeric status with isalnum. if test.isalnum(): print("isalnum: [", test, "]") else: print("false: [", test, "]")
false: [ Dot Net Perls ] isalnum: [ DotNetPerls ] false: [ Dot_Net_Perls ] isalnum: [ Dot0123 ] isalnum: [ dotnetperls ] isalnum: [ 123 ] false: [ ]
A useful method. Often we want to validate strings before putting them into a dictionary or list. Isalnum is a good method to remember—it is easier than trying to write a similar method.
Dictionary
List, strings
A review. When possible, methods like isalnum() from the standard library should be reused. They do not need testing—they are convenient and easy to understand.
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