Py Lists (Datacamp + UCSD Wk 2)

Question 1

Assign a value to a variable

Answer 1

eg, x = 5

Question 2

print values

Answer 2

print()

Question 3

Exponents in python

Answer 3

base ** exp

Question 4

find out the type of a variable

Answer 4

type(variable)

Question 5

concatenate strings

Answer 5

str3 = str1 + str2

Question 6

convert a string to a float

Answer 6

pi_float = float(“3.14”)

Question 7

convert int or float to string

Answer 7

str(int_var) or string(numerical value)

Question 8

can you multiply a string by a number?

Answer 8

Yes. “hey” * 2 = “heyhey”

Question 9

what are lists?

Answer 9

lists are arrays, and can have have various data types, including other lists

Question 10

how to assign values to a list

Answer 10

list = [var1, var2, 5, “hello”]

Question 11

how do you create a 2 dim array with lists

Answer 11

2d = [[“val1”, var1] , [“val2”, var2]]

Question 12

How do you retrieve individual elements of a list (subset)

Answer 12

list[0] (first element]; list[-1] (last element)

Question 13

How do you retrieve multiple elements from a list (slice)

Answer 13

list[1:3] - returns elements 1 and 2 (inc start, exc end)

Question 14

Do you have to specify begin and end of the indices for your list slice?

Answer 14

no. if blank, python will go to end. eg, list[ : 5] will do from begin to 5.

Question 15

specify elements from n-dim list (eg, 2 dim)

Answer 15

list [1] [2], or list [2] [0:2] - elements 0 to 2 from list 2

Question 16

how to replace list elements?

Answer 16

x[2:3] = [”s”, “t”]

Question 17

how to extend a list

Answer 17

list2 = list1 + [“e”, “f”]

Question 18

remove an element from a list

Answer 18

del( list [1] )&raquo_space; removes element 1, and renumbers all indexed elements after

Question 19

Point a new list at another list

Answer 19

newList = oldList (points to the same array)

Question 20

copy the values of a list into a new list (eg, new ind. data structure)

Answer 20

copiedList = oldList[ : ]

Question 21

append 4 to list [1,2,3] (appends an element to the end. )

Answer 21

list.append(4)

Question 22

iterate over values in a list

Answer 22

for i in list: print(i)

Question 23

iterate over list using range

Answer 23

for i in range(0, len(list)): print(list[i])

Question 24

lists are mutable

Answer 24

you can change the values in the list

Question 25

Retrieve and delete element with index 2 from a list

Answer 25

list.pop(2)&raquo_space; returns element 2, deletes, and shifts subsequent elements “down” in index

Question 26

remove an element with the value 33 from a list

Answer 26

list.remove(33)

Question 27

method to add one list to the end of an other

Answer 27

list.extend(list2)&raquo_space; (appends all the values from second list as values in first list)

Question 28

iterate through same position in two lists at same time

Answer 28

for x,y in zip(list1, list 2): print(x,” “,y)