isalnum() : Check if numbers or alphabets are only present in a string in Python

my_str.isalnum())

Checks for alphanumeric characters in a string. Returns True if only number and alphabets are present and returns False if any thing other than alphanumeric characters are present.

my_str='plus2net'
print(my_str.isalnum())      # Output is True

my_str='Welcome to plus2net'
print(my_str.isalnum())      # Output is False (presence of Space)

More using special chars

print('plus2net'.isalnum())   # True  2 is allowed  
print('_plus2net'.isalnum())  #False  _ not allowed
print('plus_2net'.isalnum())  #False  _ not allowed
print('plus.2net'.isalnum())  #False  . not allowed
print('plus-2net'.isalnum())  #False  - not allowed
print('plus@2net'.isalnum())  #False  @ not allowed
print('plus#2net'.isalnum())  #False  # not allowed
print('plus 2net'.isalnum())  #False  space not allowed

Validating userid

In any signup or login form , the userid input is to be checked then isalumn() function can be used.
Here is a code which checks the length and if the input string and is alphanumeric or not. If any condition fails then the flag used for checking became False.

if(len(userid) <5 or len(userid)>12 or not userid.isalnum()):
            flag_validation=False

Read the full script at Login Registration system.
All String methods

isalpha() isdecimal() Python- Tutorials

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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