How to Generate String Verification in Python

In this article, we show how to perform string verification in Python.

With Python, we can check if an input entered in by a user is only alphabetical characters, a number, a decimal, an integer, is a space, or is a title.

When a user enters in an input in Python through the input() function, all of the contents are considered a string.

Depending on the information being asked of the user determines what verification should be done.

For example, when you ask a person for his or her name, there should only be alphabetical characters. Therefore, we verify that all characters entered in are alphabetical characters. For example, no numbers or special symbols should be entered in. If there are, this is unacceptable input and the user should re-enter in the information correctly.

If asking for a user's zip code, all numbers should be entered in.

How to Check if a String is Composed of All Alphabetical Characters

We'll first go over how to check to see if a string is all alphabetical characters.

We do this through the isalpha() function.

The code below uses the isalpha() function to check to see if the input entered in is all alphabetical characters or not.

>>> name= "David" >>> name.isalpha() True >>> name2= "Peter1" >>> name2.isalpha() False

You can see that "David" is all alphabetical characters. Thus, "True" is output. "Peter1" is not all alphabetical characters, so "False" is returned.

How to Check if a String is Composed of All Numbers

Now we will check to see if a string is composed of all numbers.

This can be done through the isalnum() function.

This is shown in the code below.

>>> userinput="12345" >>> userinput.isnumeric() True >>> userinput2= "12345abc" >>> userinput2.isnumeric() False

Thus, userinput returns true with the isnumeric() function because it is all numbers, while userinput2 returns false because it also has alphabetical characters.

How to Check if a String is all Alphabetical Characters and Numbers

We'll now show how to check if a string only contains alphabetical characters and numbers.

We do this through the isalnum() function.

This is shown in the code below.

>>> input1= "123" >>> input1.isalnum() True >>> input2="123abc" >>> input2.isalnum() True >>> input3="123abc!" >>> input3.isalnum() False

So, you can see how the isalnum() function returns true only if the string contains only alphabetical characters and numbers.

Below can be a real-world script of a string being verified to see if it only contains alphabetical characters. This is so that you can get a sense of how a string may be verified in a real-life sort of like script.

print("Enter your name") name= input() if (name.isalpha() == True): print("This is a valid name") else: print("This is not a valid name")

Below is a table of other functions that can be used to verify a string.

Function	Description
isspace()	Returns True if the string consists only of spaces, tabs, and newlines and is not blank
istitle()	Returns True if the string consists only of words where the first letter is capatalized and the rest are lowercase
startswith()	Returns True if the string starts with whatever string you enter into its parameter
endswith()	Returns True if the string starts with whatever string you enter into its parameter

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