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Daniel Nogueira
Daniel Nogueira

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Validating Types and Data in Python

We can find out the type of a variable using the type() function, that allows us to check what type of variable the algorithm will accept or not.

Let's read a variable that's not being converted to an integer, so it's a string:

x = input('Type something: ')
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Then we run the type() function inside the print() function, to display the type of the variable x on the screen:

print(type(x))
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The result will be:

<class 'str'>
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Basic validation

Here is a brief validation of the variable, if it's not int, the code will execute the programmed condition:

if type(x) != int:
    print('The variable is not integer')
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Advanced validation

We can get so much more informations from a variable in the program, just run some of the methods:

#Contains only letters?
isalpha()

#Contains only spaces?
isspace()

#Contains only numbers?
isnumeric()

#Contains only uppercase?
isupper()

#Contains only lowercase?
lower()

#Contains only letters and numbers?
isalnum()

#First capital and others lowercase?
istitle()
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The result returned will be True or False.

Let's run the methods with a y variable:

print('Only letters?', y.isalpha())

print('Only spaces?', y.isspace())

print('Only numbers?', y.isnumeric())

print('Upper case only?', y.isupper())

print('Lower case only?', y.islower())

print('Is it capitalized?', y.istitle())

print('Letters and numbers only', y.isalnum())
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Try entering different inputs until you fully understand the concepts of each method.

In practice

We can, for example, use the isnumeric() method to validate a Zip Code. In which the program will proceed when the user enters only numbers.

Or use the istitle() method to check the Name field of a form. If the name entered is not capitalized, we can validate and even make the necessary changes to the variable.

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