On week two of the open labs, we continued building on the starter kit and worked on python data structures. We discussed loops (both for and while), dictionaries and dictionary methods.
A while loop is a concept that, when implemented, executes a piece of code over and over again, while a given condition remains true:
When constructing a while loop, you have to ensure that it has all three of the following elements:
- The while keyword
- A condition that translates to either true or false
- A block of code you want to repeat
Example:
# Input/pick a random number
number = 2
# Set the condition of the while loop
while number < 5 :
print(“Thank you”)
# Increment the value of the variable “number by 1”
number = number+1
When you run this code you produce the following result:
Thank you
Thank you
Thank you
For loop:
The for loop is used to iterate over elements of a sequence, it is often used when you have a piece of code which you want to repeat “x” number of times:
Example:
Let’s say you have a list:
fresh_fruits = [“Apple”, “Banana”, “Peach”, “Strawberry”]
for fruits in fresh_fruits:
print fruits
That means, for every element that we assign the variable fruits, in the list fresh_fruits, print out the variable fruits.
- Dictionaries
Dictionaries are similar to what their name suggests – a dictionary. In a dictionary, you have an ‘index’ of words, and for each of them a definition. In python, the word is called a ‘key’, and the definition a ‘value’. The values in a dictionary aren’t numbered – tare similar to what their name suggests – a dictionary. In a dictionary, you have an ‘index’ of words, and for each of them a definition. In python, the word is called a ‘key’, and the definition a ‘value’. The values in a dictionary aren’t numbered – they aren’t in any specific order, either – the key does the same thing. You can add, remove, and modify the values in dictionaries. Example: telephone book.
In the Python dictionary, each key is separated from its value by a colon (:), the items are separated by commas, and the whole thing is enclosed in curly braces.
An empty dictionary without any items is written with just two curly braces, like this: {}. Keys within a dictionary must be a data type such as strings, numbers, or tuples.
Example:
dict = {‘Name’: ‘Michael’, ‘Age’: 7, ‘Class’: ‘First’}
print “dict[‘Name’]: “, dict[‘Name’]
print “dict[‘Age’]: “, dict[‘Age’]
When we run this code, it produces the following result:
dict[‘Name’]: Michael
dict[‘Age’]: 7
Dictionary Methods:
- clear(): Removes all items from the dictionary in place
- copy(): Returns a new dictionary with the same contents
- fromkeys(): creates a new dictionary from the given keys
- get(): A way to access dictionary elements. Returns None when element not present in the dictionary.
- has_key(): boolean method to check if a key is present in the dictionary
- pop(): returns value corresponding to the key and also removes the pair from the dictionary
- popitem(): pops out a random item from the dictionary