MIT 6.00 Week 2

Question 1

What guarantees that a loop will end?

Answer 1

A decrementing function

Question 2

What characteristics are required of a decrementing function?

Answer 2

1) It maps a set of program variables to an integer.
2) It starts with a non-negative value.
3) It terminates when the value < 0.
4) It decreases each iteration.

Question 3

What is “brute force” problem solving?

Answer 3

Exhaustive enumeration

Determining the range of values that an answer could be, and checking each value individually, in order, until you find the correct answer.

Question 4

What is the syntax of a for loop in Python?

Answer 4

for variable in (something):

Question 5

what is the syntax for the range function?

Answer 5

range(start, stop, increment)
start is inclusive
stop is non inclusive

Question 6

What do we do when an exact answer cannot be ensured?

Answer 6

Use approximation.

Determine what answer will be close enough that we are satisfied, and search for an answer within that range.

Question 7

What is a faster type of search than exhaustive enumeration, and how does it work?

Answer 7

Bisection Search:

1) Determine a range within the answer can be found
2) Test the middle of the range. If it is too high, make it the new upper bound. If it is too low, make it the new lower bound.
3) Test the answer that is the middle of the new range.
4) Repeat until the answer, or an acceptable approximation, is found.

Question 8

What advantages does the use of functions provide?

Answer 8

1) Decomposition

2) Abstraction

Question 9

What do we mean by decomposition?

Answer 9

Structure is created. The modules created by functions are self-contained and reusable.

Question 10

What doe we mean by abstraction?

Answer 10

Details are suppressed when they are unimportant or distracting.

Question 11

How do we create a function?

Answer 11

def functionName(parameter, parameter,...):
     Function Body

Question 12

How do we get a value back from a function?

Answer 12

the return keyword

Question 13

What happens if you do not use return in a function?

Answer 13

It will return the none data type

Question 14

What is the term for calling on a function?

Answer 14

Invoking

Question 15

What is the written description and explanation of a function called?

Answer 15

The specification

Question 16

What should be included in specification?

Answer 16

The purpose/effect of the function, and the parameters it takes.

Question 17

What is the term for the parameter found in the definition of a function?

Answer 17

The formal parameter

or

parameter

Question 18

What is the term for a value passed into a function?

Answer 18

The actual parameter

or

argument

Question 19

What is scope?

Answer 19

The matching of names to objects.

Question 20

What keyword will check for a true/false value, and terminate the program is the value is false?

Answer 20

assert

Question 21

Planning for bad inputs is:

Answer 21

Defensive programming

Question 22

When are scopes created?

Answer 22

When a function is run, not when it is defined.

Question 23

Another term for scope is:

Answer 23

A stack frame

Question 24

The list of scopes and their relative distance to the main scope:

Answer 24

The stack

Question 25

When something is removed from the stack, we:

Answer 25

pop the stack

Question 26

What is the relationship of variables in one scope to the variables of another scope?

Answer 26

They are discreet.

This is more complicated than it is currently being presented.

Question 27

What happens if a string is used in a for loop?

Answer 27

The variable will be assigned each character in the string, in order, and run through the loop.

Question 28

How do you find a character in a certain position within a string?

Answer 28

s[#:#]

where “s” is the name of the variable the string is in, the first # is the position of the character you want to start with, and the second # is the end character.

The first number is inclusive, starting at 0. The second number is exclusive.

Question 29

How do you find a certain character in a string?

Answer 29

variableName.find(‘a’)

‘a’ is the character you are looking for. The result is the position of the character in the string, starting with 0.

Question 30

How do you find a list of everything you can do with a data type, without descriptions?

Answer 30

dir(data_type)

Question 31

How do you find a definition of a keyword from within IDLE?

Answer 31

help(data_type.keyword)

Question 32

how do you find a list of everything you can do with a data type, with descriptions?

Answer 32

help(data_type)

Question 33

Define a tuple:

Answer 33

a non-scalar data type that can hold many things

Question 34

what is the literal syntax of a tuple?

Answer 34

(element, element)

Question 35

How can the individual parts of a tuple be accessed?

Answer 35

By using indices

Question 36

what are two ways to print an individual element of a tuple?

Answer 36

print tuple_name[x]
Where x is the index position you want to print, starting with 0

print tuple_name[-x]
Where -x is the index position you want to print, reading from right to left, starting with -1 as the last element in the tuple.

Question 37

What kind of data structure only houses one kind of data type?

Answer 37

A homogenous data type

Question 38

What kind of data structure houses multiple different data types?

Answer 38

A heterogenous data structure.

Question 39

Tuples can hold tuples

Answer 39

tuple_name1(tuple_name2(x, y), z)

Question 40

What happens if you print the tuple itself?

Answer 40

You will print a literal representation of the tuple, as you see it.

if the tuple is (1, 2, ‘a’), the program will print:

(1, 2, ‘a’)

Question 41

A data type whose elements cannot be changed is an:

Answer 41

immutable data type

Question 42

Are tuples an immutable data type?

Answer 42

yes

Question 43

What are the defaults when you leave blanks while choosing sections of an index? i.e. [:#] or [#:]

Answer 43

The default start is 0

the default end is the last element of the index

Question 44

What happens when you add a tuple to a tuple?

Answer 44

The elements of the second tuple are added, in order, to the end of the first tuple.

Question 45

What is a common mistake when writing a tuple of one element?

Answer 45

Forgetting the ‘,’

For example (‘a’,) is a tuple, whereas (‘a’) is not. The second is simply regarded as more important for order of operations.

Question 46

What keyword kicks you out of a loop?

Answer 46

break

Question 47

What is a function, roughly?

Answer 47

A named, pre-written piece of code that takes inputs and gives outputs.

Question 48

What is another term for the specification?

Answer 48

The doc string

Question 49

What is another term for invoking a function?

Answer 49

Calling the function