Lecture 12 — Solving Problems on Lists

In today’s lecture we solve a few problems on lists to understand the concept of lists better.

Overview of Today

  • List functions and Methods

  • Nested lists OR

  • Lists of lists

Additional Methods

Today we will also talk about a few more methods that work on lists and strings:

Converting Strings to Lists

  • Method 1: use function list() to create a list of the characters in the string.

  • Method 2: use the string split() function, which breaks a string up into a list of strings based on the character provided as the argument.

    • The default is ' '.

    • Other common splitting characters are ',', '|' and '\t'.

  • We will explore with the s = "Hello world" example in class.

Converting Lists to Strings

  • What happens when we type the following?

    >>> s = "Hello world"
>>> t = list(s)
>>> s1 = str(t)

    This will not concatenate all the strings in the list (assuming they are strings).

  • We can write a for loop to do this, but Python provides something simpler that works:

    >>> L1 = ['Hello', 'World']
>>> print(''.join(L1))
HelloWorld
>>> print(' '.join(L1))
Hello World