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11112017, 02:32 AM #1
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 Nov 2017
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Trying to change what are in variable slots to no success
I have been learning to use the 3.5.2 python shell and have been confused about how python stores variables in memory. After I change what is stored in some variables, how do I make change what is in the empty variable slots in a string variable?
I first assign three integers to three variables.
>>>num1 = 6
>>>num2 = 7
>>>num3 = 8
I then assign a string to a variable that has three empty variable slots.
>>>list_of_numbers = "Here is a list of three numbers: {}, {}, and {}"
I then use the format function to place the three integers in to the empty variable slots.
>>>list_of_numbers= list_of_numbers.format(num1, num2, num3)
When I ask for a read out of list_of_numbers I, of course, get:
>>>list_of_numbers
'Here is a list of three numbers: 6, 7, and 8'
The problem arises when I assign new integers to num1, num2, and num3.
>>>num1 = 12
>>>num2 = 14
>>>num3 = 28
Because I have changed what is stored in num1, num2, and num3, I attempt to use the format function to assign the new variables to the string list_of_numbers.
>>>list_of_numbers = list_of_numbers.format(num1, num2, num3)
When I ask for a read out of list_of_numbers I get this:
>>>list_of_numbers
'Here is a list of three numbers: 6, 7, and 8'
Why doesn't the interpreter change what what variables are filled in list_of_numbers? I know the CPU has assigned new integers to the variables num1, num2, and num3. So why can't I change what variables are listed in list_of_numbers?

11112017, 11:31 AM #2
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 Oct 2015
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When you try to change the string the second time, it equals
'Here is a list of three numbers: 6, 7, and 8' and not 'Here is a list of three numbers: {}, {}, and {}' so the interpreter does not see where to make the replacements.
Code:>>>num1 = 6 >>>num2 = 7 >>>num3 = 8 >>>list_of_numbers = "Here is a list of three numbers: {}, {}, and {}" >>>list_of_numbers= list_of_numbers.format(num1, num2, num3) >>>list_of_numbers 'Here is a list of three numbers: 6, 7, and 8' >>>num1 = 12 >>>num2 = 14 >>>num3 = 28 >>>list_of_numbers = "Here is a list of three numbers: {}, {}, and {}" # reset the string with placeholders >>>list_of_numbers = list_of_numbers.format(num1, num2, num3) >>>list_of_numbers 'Here is a list of three numbers: 12, 14, and 28'