week 9 functions with lists Flashcards
defining lists
can be hardcoded, list function, or from a file
mutable types in functions
list, dictionary, and set that are passed into function are also altered in the workspace
index method
allows you to search ordered object for certain value and returns the index
expense
the number of comparisons needed to find something (in reference to methods)
ordering/sorting data
increases efficiency because you know where stuff is and can select certain chunks to search for something
binary search
reducing search items by sorting data
scope
part of a program that variable/function exists
local variables
variables defined in functions, the scope is within the function
global variable
created outside function, scope is from defining statement until the end of the file
global statement
used to change a global value and create a global value inside a function (use keyword global, then state function name)
do modifications to mutable types within a function need a global statement?
no
function scope
from function definition until the end of the file
namespace
maps names to objects
locals()
prints all local variables
globals()
prints all global variables
3 nested scopes
built-in scope, local scope, global scope
built-in scope
contains built-in python names, like int, str, list, etc
scope resolution
process of searching for object name in available namespaces
order of scope resolution
local, global, built-in
pass-by-assignment
when the function is called, new local variables are created in the function’s local namespace, parameter names are binded to the passed arguments
immutable objects
modifications are limited to function
mutable object
modifications affect the full scope
how do you avoid changes to mutable objects in functions?
create a copy of the object
ex:
copy = item_list[:]
list
mutable container with sequential order, elements can be accessed through indexing
in-place modifications
elements can be added or removed at any time
list methods
operations to add or remove elements to a list, lists can also be sorted or reversed
insert method example
list.insert(1, ‘string’) –> adds new element, ‘string’, at index one
for loop
can iterate over each element of a list
index error
trying to access an index out of range
enumerate()
function that iterates over a list and provides an iteration counter
all(list)
true if there are no 0s in list
any(list)
true if any element of list is true
max(list)
returns max, same structure for min and sum
list nesting
list of lists
how do you index nested lists
my_list[0][0] –> returns 1st element of 1st list in my_list
multidimensional data structure
data structure that contains more layers of data
nested for loops
can be used to access elements of nested lists
slice notation
read multiple items from list and create new one with desired elements
stride
step size for indexing and accessing elements
my_list[start:end:stride]
sorted()
sorts list and makes copy instead of modifying existing
list method key
argument that specifies a function to be applied to each element before comparing
how do you use sorted function with lowercase key?
sorted(names, key=str.lower)
how do you use sorted function with reverse key?
sorted(names, reverse=True)
