String isalnum Example
This page was last reviewed on Oct 9, 2021.
Dot Net Perls
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.
Detail 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).
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.
String List
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.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Oct 9, 2021 (edit).
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