For the second lesson, we looked at:<\/p>\n\n\n\n
{\"Shreya\": 55, \"Nandini\": 72}<\/code><\/li>- Dictionary variable:
a = {\"Shreya\": 55, \"Nandini\": 72}<\/code><\/li>- Dictionary read\/access:
a[\"Shreya\"]<\/code><\/li>- Dictionary write\/assignment:
a[\"Shreya\"] = 22<\/code><\/li>- Dictionary has-key test:
\"Shreya\" in a<\/code> => (read “yields” or “outputs” or “returns”) True<\/code>, \"Fred\" in a<\/code> => False<\/code><\/li><\/ul><\/li>- Functions
- Defining a function:
def functionName(parameter1, p2, p3 = \"default value\"):<\/code>- The “body” of the function needs to be indented.<\/li>
- Default values can be provided when defining function parameters, but if a parameter has a default value, then all parameters after it must also have default values, so that there is an easy rule for matching arguments to a function with the right parameter\/container\/variable name.<\/li><\/ul><\/li>
- Aside:<\/em> Any line following a colon (:) must be indented. When the indentation stops, this signifies the end of that “body” of code. E.g. if-then-else statements looks like this:
if a[\"Shreya\"] > a[\"Fred\"]:<\/code>print(\"Give cane to Shreya\")<\/code><\/li><\/ul><\/li>else:<\/code>print(\"Give cane to Fred\")<\/code><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/li>- Classes
- Classes provide a nice way to organize programming code. Intuitively, they match concepts and words that we use in real life, like Person, Car, Address, Phone Number, etc.<\/li>
- Classes usually define both a set of variables that each “instance” of the class will have and a set of functions that can be used to get information about or change information about an instance of that class.
- Variables: E.g. all Persons shall have a name and password, and all Cars shall have a position and a heading\/direction, etc.<\/li>
- Functions (called “methods”): E.g. all Persons shall have a function that combines their first name and last name using the rule lastName + “,” + firstName, and all Cars shall have a function that moves it in the direction it is facing by 10 steps.<\/li><\/ul><\/li>
- Classes in Python are defined as follows:
def Person:<\/code>def __init__(self, firstName, lastName):<\/code>self.firstName = firstName<\/code><\/li>self.lastName = lastName<\/code><\/li><\/ul><\/li>def lastNameCommaFirst(self):<\/code>return self.lastName + \", \" + self.firstName<\/code><\/li><\/ul><\/li><\/ul><\/li>- This is really shorthand for:
- Define a class type called “Person”, and define a “constructor” function that does something like this function:<\/li>
def Person(firstName, lastName):<\/code>person = new Person()<\/code><\/li>Person.__init__(person, firstName, lastName)<\/code><\/li>return person<\/code><\/li><\/ul><\/li>- Where
Person.__init__<\/code> is the full name of the __init__<\/code> function we defined.<\/li>- If we create a Person and assign them to a variable called myFriend,
myFriend = Person(\"Bunny\", \"Hopscotch\")<\/code>, then we could get the string \"Hopscotch, Bunny\"<\/code> from myFriend by typing myFriend.lastNameCommaFirst()<\/code>.- Note that
myFriend.lastNameCommaFirst()<\/code> gets converted internally to Person.lastNameCommaFirst(myFriend)<\/code>, hence the “self” in the definition. People just prefer to type myFriend.lastNameCommaFirst() <\/code>over Person.lastNameCommaFirst(myFriend)<\/code>.<\/li><\/ul><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
For the second lesson, we looked at: Dictionaries Dictionary literal: {“Shreya”: 55, “Nandini”: 72} Dictionary variable: a = {“Shreya”: 55, “Nandini”: 72} Dictionary read\/access: a[“Shreya”] Dictionary write\/assignment: a[“Shreya”] = 22 Dictionary has-key test: “Shreya” in a => (read “yields” or “outputs” or “returns”) True, “Fred” in a => False Functions Defining a function: def functionName(parameter1, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":46,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-48","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/pages\/48","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/comments?post=48"}],"version-history":[{"count":6,"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/pages\/48\/revisions"}],"predecessor-version":[{"id":80,"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/pages\/48\/revisions\/80"}],"up":[{"embeddable":true,"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/pages\/46"}],"wp:attachment":[{"href":"https:\/\/www.mercerislandtech.com\/index.php\/wp-json\/wp\/v2\/media?parent=48"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}