How Do We Read A List From The Keyboard?

We can read the values of a list and store them in a data collection of our program (a variable of type list).

EXAMPLE
Analyze the following program:

double_arrow Execute  hourglass_top Execute

clear    cached    undo    redo

Console / Output

done

error_outline

clear

Mind the syntax!

DETAILS
Initially, the list is empty. At each step, an element is added using the append() method, as previously presented. At the end, the entire list is displayed.

We could have written the add statement more elegantly like this:

lista.append(input('element ' + str(x)+ ' = '))

and reading the data would have been cooler:


Running the program offline, in Python IDLE

If we want the list elements to contain only numbers, we use explicit conversion, for example to real numbers (class float):

lista.append( float(input('element ' + str(x)+ ' = ')) )

You should warn the user with an appropriate message. If they enter a value that is not numeric, the program will immediately return an error - a text cannot be converted to a real number, right?

Moreover, you can also add elements using the insert(index,value) method, as it suits you...

A List With A Variable Number Of Elements?

Well ... the for loop is out of the question then! We use while, with a stop condition - for example, when the entered element is empty (just press the Enter key):

lst = []
# first read a value to be read
value = input()
# repeat while nothing is read
while value != "":
    lst.append(value)
    value = input()
# finally, display the list
print(lst)

1

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