CSC111 Lab 4 2015b

--D. Thiebaut (talk) 15:21, 27 September 2015 (EDT)

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String Slices

• Use Python in interactive mode and try the following Python statements. Try to figure out the answers to the questions.

Python 3.5.0b1 (v3.5.0b1:071fefbb5e3d, May 23 2015, 18:22:54) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "copyright", "credits" or "license()" for more information.
>>> a = "H:/English103/paper1.doc"
>>> a

>>> len( a )

>>> a[0 : 2]

>>> a[3 : 13]

>>> a[-3 : -1]

>>> a[-5 : -1]

>>> a[-5 : ]                  (no, I didn't forget the second number!)

>>> a[ : 3]                   (and no again, I didn't forget the first number!)

>>> a[3 : -3]

>>> b = "C:/My Documents/paper2.htm"

You will have discovered that both a and b contain strings representing the name of files on a computer.

Question 4

What slice that will return the drive information for a (i.e. 'H:')? If you replace a by b, does your statement still return the drive for b? If not, figure out a way to take the slice that works independently of the string a, or b.

Question 5

What is the slice that will return the extension of a (i.e. doc)? If you replace a by b in your statement, do you get the extension of b? If not, figure out a way to write the slice that will work independently of the length of the file name.

Question 6

Once you have figured out the answers to Question 2, write a simple Python program that asks the user for a file name, such as the ones we used for a or b above, and that replaces the extension with the string "txt". Your program should display the final string, as illustrated below. Make sure you put your program in a main() function (a good reflex to start having!)

Example

Filename? C:/My Documents/paper02182010.doc

C:/My Documents/paper02182010.txt