Python exercises: Strings

Note Some of the exercises below are adapted from the Python for Everyone Course by Charles R. Severance licensed under Creative Commons Attribution 3.0

Exercise 1. Extract substring

Take the following Python code that stores a string:

text1 = 'X-DSPAM-Confidence:0.8475'

Use find and string slicing to extract the portion of the string after the colon character and then use the float function to convert the extracted string into a floating point number.

text1 = 'X-DSPAM-Confidence:0.8475'
# your code here

Exercise 2. Understanding string methods

Read the documentation of the string methods here. You might want to experiment with some of them to make sure you understand how they work. Strip and replace are particularly useful.

The documentation uses a syntax that might be confusing. For example, in find(sub[, start[, end]]), the brackets indicate optional arguments. So sub is required, but start is optional, and if you include start, then end is optional.

Then use these commands to remove leading, trailing and double spaces (iteratively) in the string indicated below and replace the word “setece” with “sentence”.

text2 = "  This is a  setece      with  a typo and   too many  spaces "
# your code here

Exercise 3. Create a looping text

Adapt the program you wrote in the previous chapter to present a moving text of 40 characters long that runs like a circle from left to right: when characters reach the end they starts to appear at the beginning again.

Work step by step!

  • If you do not know where to start, assume you want to print the string “1234” and write out what should be the values (use a piece of paper!), like this sketch:

  • If the script works for “1234”, you can change the code to make it work for a string of any length e.g. “Look at this moving text!!!!!!!!!!!!!!!!” (40 characters long).

  • If this works, repeat the loop for 3 cycles (add an outer loop that runs 3 times)

# your code here