Object Types

Question 1

What are the built-in object types?

Answer 1

Numbers, strings, lists, dictionaries, tuples, files, sets

Question 2

For a sequence type, what does the [index] operator do?

Answer 2

Returns the index-th element. Zero-based.

Question 3

For a sequence type, what does the [-index] operator do?

Answer 3

Returns items from the end of the sequence. -1 is the last item, and so on.

Question 4

How do you create slices with sequences?

Answer 4

S[1:3]

Question 5

How do you get the length of a string?

Answer 5

len(S)

Question 6

How do you get everything from the 2nd character to the end?

Answer 6

S[1:]

Question 7

How do you concatenate strings?

Answer 7

s1 + s2

Question 8

How do you create repeated strings

Answer 8

‘Spam’ * 8

Question 9

Are strings mutable?

Answer 9

Nope. Modify, then copy.

Question 10

How do you find the position of substrings?

Answer 10

S.find(‘pa’)

Question 11

How do you find and replace in strings?

Answer 11

S.replace(‘pa’, ‘xyz’)

Question 12

How do you remove whitespace from the right of a string?

Answer 12

S.rstrip()

Question 13

How do you get a list of attributes for an object?

Answer 13

dir(object)

Question 14

What do you import to do pattern matching?

Answer 14

import re

Question 15

What is a list?

Answer 15

A mutable sequence.

Question 16

How do you initialize a list?

Answer 16

L = [a, b, c]

Question 17

How do you add an element to the end of a list?

Answer 17

L.append(ele)

Question 18

How do you remove an element from the list?

Answer 18

L.pop(position)

Question 19

How do you sort a list?

Answer 19

L.sort()

Question 20

How do you reverse the order of a list?

Answer 20

L.reverse()

Question 21

What is nesting?

Answer 21

containing one object inside another. A list that contains lists, for example.

Question 22

What are list comprehensions?

Answer 22

Complicated but probably useful for matrix operations. Out of scope.

Question 23

What is a dictionary?

Answer 23

A set of key->value mappings.

Question 24

How do you initialize a dictionary?

Answer 24

D = {‘key1’, ‘value1’, ‘key2’, ‘value2’ }

Question 25

How do you retrieve a key’s value from a dictionary?

Answer 25

D[‘key’]

Question 26

How do you create a new key/value pair in a dictionary?

Answer 26

Just assign it as D[‘key’] = ‘value’

Question 27

How do you test for an object not being in a dictionary?

Answer 27

if not ‘f’ in D:

code

Question 28

What is a tuple?

Answer 28

An immutable list, used to represent fixed collections of items.

Question 29

How do you code tuples?

Answer 29

(a, b, c). Contrast with a list: [a,b,c]

Question 30

How to you open a file?

Answer 30

f = open(‘filename’, ‘w’)

Question 31

How do you write to a file?

Answer 31

f.write(‘text’)

Question 32

How do you close a file?

Answer 32

f.close()

Question 33

How do you read from a file?

Answer 33

text = f.read()

Question 34

What is a set?

Answer 34

An unordered collection of immutable objects

Question 35

How do you initailize a set?

Answer 35

Y = {‘h’, ‘a’, ‘m’}

Question 36

How can you compute with decimal numbers?

Answer 36

import decimal

d = decimal.Decimal(‘3.1.415’)

Question 37

How can you compute with fractions?

Answer 37

from fractions import Fraction

f = Fraction(2,3)

Question 38

When are variables created?

Answer 38

When they are assigned.

Question 39

How do you create a variable without assigning it?

Answer 39

You can’t.

Question 40

How do you create comments in python?

Answer 40

comment…

Question 41

How do you create random numbers?

Answer 41

import random

random.random()

Question 42

How do you create random integers in a range?

Answer 42

import random

random.randint(1, 10)

Question 43

How do you randomly select an item?

Answer 43

import random

random.choice([‘a’, ‘b’, ‘c’])

Question 44

Where can you get advanced numeric methods?

Answer 44

NumPy