ch 8 practice questions

Question 1

How many times is the letter ‘r’ printed below?

s = “strawberry”
idx = 1
while idx < len(s):
print(s[idx])
idx = idx + 2

Answer 1

1

Question 2

What is printed?

s = “Ball”
s[0] = “C”
print(s)

Answer 2

Nothing, error

Question 3

what does .find() do?

Answer 3

searches for the position of one string within another

it can also take a second index as to where it should start looking
ex. .find(‘na’, 3)

Question 4

what does the following print?

line = ‘Have a nice day’
print(line.lower().startswith(‘h’))

Answer 4

True

Question 5

What is printed?

s = “let’s go blue!”
print(s.count(“e”) + s.count(“b”))

Answer 5

3

Question 6

What is parsing?

Answer 6

looking into a string and finding a substring

Question 7

what types are the following used for?
1. %d
2. %g
3. %s

Answer 7

integer
floating point number
string

Question 8

what does format operator % do?

Answer 8

allows us to construct strings, replacing parts of the strings with the data stored in variables; when operand is a string, % is the format operator

Question 9

What is returned by the following?

str = “His shirt is red”
pos = str.find(“is”)
print(pos)

Answer 9

1; gives back 1st position of argument

Question 10

What is printed by the following?

s1 = “heY”
s1 = s1.capitalize()

Answer 10

Hey
capitalize only uppercases the first letter

Question 11

How do you know when ‘open’ is sucessful?

Answer 11

the system returns a file handle object, something that we can use to read data

Question 12

What is a file handle?

Answer 12

an object used to read/ modify a file, not the actual data in the file

Question 13

what is \n?

Answer 13

newline, breaks whatever ur typing into 2 lines
it counts as its own character

Question 14

If you know the file is relatively small compared to the size of your main memory, you can read the whole file into one string using what?

Answer 14

read method; .read()

Question 15

What is the difference between the 2 codes?

1)
fhand = open(‘mbox-short.txt’)
for line in fhand:
if line.startswith(‘From:’):
print(line)
fhand.close()

2)
fhand = open(‘mbox-short.txt’)
for line in fhand:
line = line.rstrip()
if line.startswith(‘From:’):
print(line)
fhand.close()

Answer 15

2) has line.strip(), which gets rid of the default newline in code 1

Question 16

rstrip vs strip?

Answer 16

rstrip removes whitespace from the right side of the str, strip removes whitespace from left and right side of str

Question 17

when ‘find’ returns a negative value, what does this mean?

Answer 17

the value could not be found

Question 18

What parameters do you need for for the write function

Answer 18

filename and ‘w’

Question 19

what does the write method do?

Answer 19

handle object puts data into the file, returning the number of characters written

Question 20

why do you need the close functions?

Answer 20

to make sure that the last bit of data is physically written to the disk so it will not be lost if the power goes off

Question 21

what does repr do?

Answer 21

takes any object as an argument and returns a string representation of the object

ex.
s = ‘1 2\t 3\n 4’
print(repr(s))

‘1 2\t 3\n 4’

Question 22

What opening file format closes the file automatically when you leave the bock (indented area)?

Answer 22

with open(file) as name:

Question 23

What is printed by the following? Why

print(‘ “1958”‘.strip(‘”’))

Answer 23

“1985

strip() removes both leading and trailing whitespace. Since you didn’t add a space before the quotes, it won’t remove the leading “