Week 10 Lab Exercise - Hsu Users Web Pages (Page 2 of 3) in pdf

CIS 130 - Intro to Programming

p. 2

Week 10 Lab Exercise - 03-28-07

You want to write 27 to this file, but also a newline character. Write a Python statement below that will do

so.

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And, write a Python statement that will now close this file.

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10. Now, on to arrays/lists! Write a Python statement that will set the variable listy to be a list containing the

values 1, 3, 15, and 8.

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11. You decide you want to add 23 to list listy. Write a Python statement that will do so.

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12. You find that you need to change the value 3 in this list to instead be 13. Write a Python statement that will

do so.

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13. Three more items are added to listy (so that now it contains 8 items in all). Write a Python statement that

will print JUST the last element of the list listy.

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14. And, write a Python statement that will print the entire list listy.

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15. You can probably imagine that it is occasionally useful to read numbers from a file into a list.

Write a function read_nums that takes a string as argument, the name of a file in the current directory

expected to contain one integer per line. The function opens the file and reads its contents into a list, and

then returns a list of the numbers in this file as its result.

(Be careful -- the list should be a list of numbers, not a list of strings. How can you obtain the number

equivalent to a number-formatted string (read from the file)? Note that it turns out that this means will also

happily eliminate that pesky newline from the end of the string read...)

In the interests of lab time, I will just run your read_nums to see if it works. Create a file in the current

working directory named test.txt that contains the numbers 5, 8, 2, 7, 1, 4, and then you will show me the

results of the following when it is your turn:

read_nums("test.txt") == [5, 8, 2, 7, 1, 4]

16. Remember line_of_X from HW #5? (If not, you can remind yourself by looking at the "Some solutions"

section of the public course web page.)

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