compsci certification

IndexError

An attempt to access a non-existent list element (when the index goes out of the permissible range) raises the ___ exception

slice

means by which the programmer can create a new list using a part of the already existing list.

slicing example

my_list = [10, 20, 30, 40, 50]

print(my_list[1:4]) [20, 30, 40] (Index 4 is NOT included)

print(my_list[:3]) [10, 20, 30] (Start from 0)

print(my_list[2:]) [30, 40, 50] (Go until the end)

slicing example

the_list = [0, 1, 2, 3]

print(the_list[-3:-1])

answer: [1.2]. Just like the range, you subtract one from the end so instead of 3 it is 2.

list_b = list_a[:]

is a slicing operator in Python. It’s used to create a copy of the list, from beginning to end, which is a shorthand for copying a list.

list_a = [1]

list_b = list_a[:]

list_b[0] = 0

print(list_a[0] == list_b[0])

This is FALSE, because it changes the b(1) to a b(0) and since a does not have a 0, and 0 is not equal to 1, it is false.

the_list = []

the_list.append(1)

print(the_list)

It appended, or added one to the list

the_list = [1]

the_list.insert(0, 2)

print(the_list)

answer: [2,1]

the 0 tells you what place to put the 2. So then the 0 is replaced with the 2 from the 1, pushing it to the right and giving you [2,1]

the_list = [1, 'a']

print('a' in the_list, 1 not in the_list)

would give you true and false because a and 1 are both in the list

5. Strings and tuples are immutable and their contents cannot be changed.

yea

error that comes when trying to add or take away from a tuple

TypeError

1. An attempt to access a non-existent tuple element raises the __ exception.

Index error

An attempt to access an element whose key is absent in the dictionary raises the__ exception

KeyError

1. Function definition must precede its invocation. Breaking this rule raises the ____ exception.

NameError

def function(a, b, c):

print(a, b, c)

function(1, c=3, b=2)

answer: 1 2 3

function(1, a=1, b=2)

TypeError

scope

part of the code where a certain name is properly recognizable.

def function(parameter):

parameter = [2]

the_list = [1]

function(the_list)

print(the_list)

1

def function(parameter):

parameter[0] = 2

the_list = [1]

function(the_list)

print(the_list)

2

def process (data):

data=[1,2,3]

return data[-2]

measurements = [0 for i in range (3)]

process(measurements)

print(measurements[-2])

0 → only pay attention to the measurements part which has a range of three, 0,0,0

def process (data):

data[1]=2

return data[-2]

measurements = [0 for i in range (3)]

process(measurements)

print(measurements[-2])

changes the 0,0,0 to 0,2,0 and it asks for -2 value so answer is 2

def combine(width, height=2, depth=0, is_3D= False):

return(is_3D, width, height, depth)

print(combine(1)[2])

so width is 1 and it returns a tuple seen in the parenthesis. Then, according to this the order is False, 1,2,0 and the {2} index of this tuple is 2

def walk(top):

if top==0:

return 0

return top+walk(top-1)

print(walk(2))

3