Computer Lab 04, Iterables

more complex data types: Strings, tuples, lists. Traversing. Basic methods.

• a weekly puzzle to train the brain

implement the following functions and test them appropriately.

def count_chars(string, char):
    """Return the number of occurances of char in string.
 
    :param string: a string. Example "hello world"
    :param char: character. Example "l"
    :return: int number of char occurences in string
    >>> count_chars("hello","l")
    2
    """

def replace_chars(string, char_original, char_replacement):
    """Return a new string with all occurences of char_original replaced by char_replacement.
 
    :param string: string in which some chars shall be replaced
    :param char_original: character to be replaced
    :param char_replacement: character to be inserted instead of char_original
    :return: a new string with replaced characters
    >>> replace_chars("hello","h","H")
    "Hello"
    """

def reverse_string(string):
    """Return a reversed version of string.
 
    :param string: string to be reversed
    :return: reversed string
    >>> reverse_string("hello")
    "olleh"
    """

def is_palindrom(string):
    """Return True if and only if the string is equal to its reversed version.
 
    :param string: string to check for palindrom
    :return: boolean
    >>> is_palindrom("aka")
    True
    >>> is_palindrom("hello")
    False
    """

def remove_duplicates(items):
    """Remove duplicate items.
 
    :param items: input list, can contain anything
    :return: (unique_list, duplicates)
        unique_list - a list with unique items only
        duplicates - a list with items that were in items more than once
    >>> remove_duplicates(['h','e','l','l','o'])
    (['h','e','l','o'],['l'])
    """

• Solve homework quadratic_equation and submit it via Upload system in time! Check the deadline in Upload system.
• The homework from last week was to read chapters 6,7,8,9 from [Wentworth2012]. Go through them once more and concentrate on things you do not understand.
• Read chapter 11 (Lists) from [Wentworth2012].