Read Allen Downey's Think Python for getting up to speed with Python 2.7 and computer science topics. It's completely available online, or you can buy a physical copy if you would like.
For quick and easy interactive practice with Python, many people enjoy Codecademy's Python track. There's also Learn Python The Hard Way and The Python Tutorial.
How are Python lists and tuples similar and different? Which will work as keys in dictionaries? Why?
Lists (which uses "[]") and Tuples (which uses "()") each contain a set of values. The main difference between a list and tuple is that a list is mutable and thus the number of values (and memory) can vary while a tuple is fixed. Only a tuple can be used as a key in a dictionary because it is immutable and is used as reference for the values in the dictionary. Every key in a dictionary has a unique hash value and since a list is mutable, if the list were to change, it would skew the dictionary and the value that was returned would be different.
How are Python lists and sets similar and different? Give examples of using both. How does performance compare between lists and sets for finding an element. Why?
A list is an group of values that is ordered (you can call individual values by their index) and may contain duplicates. A set is an unordered list and cannot contain duplicates. set: l = {'a','d','b','c','d'} --> print(l) = {'d', 'b', 'c', 'a'} list: l =['a','b','c','d','e'] --> print(i) = ['a','b','c','d','e']
If you are looking if an element exists in a list or set, the set performs better. It takes O(1) to find an element in the set compared to O(n) for the list which is linear time and takes increasingly long depending on how long the list is.
Describe Python's lambda. What is it, and what is it used for? Give at least one example, including an example of using a lambda in the key argument to sorted.
lambda is a small anonymous function that reduces the amount of scripting needed. Lambda, in the case below, allows us to reduce the amount of code needed and allows us to use a function once in another function. Example: sorted("Here is a sentence that has Capital and lowercase Letters As the first letter in The Word".split(), key=lambda word: word.lower())
Explain list comprehensions. Give examples and show equivalents with map and filter. How do their capabilities compare? Also demonstrate set comprehensions and dictionary comprehensions.
List comprehensions allow you to produce lists more efficiently.
An example of a list comprehension: numSquared = [num for num in range(10) if num % 2 ==0]
The equivalent with 'map': numSquared = list(map(lambda num: num if num % 2== 0 else None, range(10)))
The equivalent with 'filter': numSquared = list(filter(lambda num: num % 2 ==0, range(10)))
Map applies a function across a list or set of values in a very similar way to list comprehension. Filter does a similar task but removes values that return false according to the lambda statement.
Set comprehensions allow you to perform tasks on a set similar to list comprehensions. Dictionary comprehensions are similar as well but require both a key and value to be inputs.
Use Python to compute days between start and stop date.
a.
date_start = '01-02-2013'
date_stop = '07-28-2015'
937 days
b.
date_start = '12312013'
date_stop = '05282015'
513 days
c.
date_start = '15-Jan-1994'
date_stop = '14-Jul-2015'
7,850 days
Place code in this file: q5_datetime.py
Edit the 7 functions in q6_strings.py
Edit the 5 functions in q7_lists.py
Write a script as indicated (using the football data) in q8_parsing.py