Python Strings and Files: Practice Questions

For each snippet, write the output. If it prints nothing, write “No Output”.

Practice the operations from the Strings and Files reading. Use the encoding reference chart for character lookups; you may bring a printed copy to an open-note quiz. Character-code memorization and hand conversion between number bases are not required. File questions create their own input files in the current working directory.

Basic String Operations

Indexing and slicing of strings works similarly to indexing and slicing of lists. The main difference is that the type of the result when indexing/slicing a string is always another string.

Question 1

s = 'hello world'
print(s[:-6])

Answer

hello

Question 2

s = '12345' 
xs = [1, 2, 3, 4, 5]
b = s[-1] == xs[-1]
print('b=', b)

Answer

b= False

Question 3

s = 'hello'
xs = ['h', 'e', 'l', 'l', 'o']
b = s[-2:] == xs[-2:]
print('b=', b)

Answer

b= False

Question 4

s = 'python is awesome'
if 'python' in s:
    print('True')
else:
    print('False')

Answer

True

Question 5

s = 'python is awesome'
if 'Python' in s:
    print('True')
else:
    print('False')

Answer

False

Python strings support a number of methods that lists do not support. It is important to remember that strings are immutable, and so methods will never change the content of a string.

Question 6

s = 'python is awesome'
t = s.replace('python', 'everything')
print('t=', t)

Answer

t= everything is awesome

Question 7

s = 'python is awesome'
s.replace('python', 'everything')
print('s=', s)

Answer

s= python is awesome

Question 8

s = 'python is awesome'
t = s.split()
u = t[-1]
print('u=', u)

Answer

u= awesome

Question 9

s = 'python\nis\tawesome'
t = s.split()
u = ' '.join(t)
print('u=', u)

Answer

u= python is awesome

Question 10

s = 'python  is\tawesome'
t = s.split(' ')
u = t[1]
print('u=', u)

Answer

u=

Question 11

s = 'python is awesome'
t = s.split('o')
u = 'XXX'.join(t)
print('u=', u)

Answer

u= pythXXXn is awesXXXme

Question 12

s = 'guido van rossum'
i = s.find(' ')
t = s[:i]
print('t=',t)

Answer

t= guido

Question 13

s = 'guido van rossum'
i = s.find('G')
t = s[:i]
print('t=',t)

Answer

t= guido van rossu

Characters and Encodings

Question 14

print(chr(ord('a') - 32))

Answer

A

Question 15

print(chr(ord('f') - 3))

Answer

c

Question 16

s = '\x48\x45\x4C\x4C\x4F'
print('s=', s)

Answer

s= HELLO

Question 17

s = 'cat\n'
print(len(s))
print(repr(s))

Answer

4
'cat\n'

Question 18

data = 'cat'.encode('utf-8')
print(data)
print(data.decode('utf-8'))

Answer

b'cat'
cat

Question 19

text = 'café'
data = text.encode('utf-8')
print(len(text))
print(len(data))

Answer

4
5

Reading and Writing Files

Opening with mode 'w' creates or empties a file. Writing does not add a newline automatically. A with block closes the file when the block ends. Reading advances the file’s position; another read at the end returns an empty string.

Question 20

with open('poem.txt', 'w', encoding='utf-8') as f:
    f.write('cat\nmat\n')
with open('poem.txt', encoding='utf-8') as f:
    contents = f.read()
print(repr(contents))

Answer

'cat\nmat\n'

Question 21

with open('colors.txt', 'w', encoding='utf-8') as f:
    f.write('red,green,blue')
with open('colors.txt', encoding='utf-8') as f:
    colors = f.read().split(',')
print(colors[1])

Answer

green

Question 22

with open('note.txt', 'w', encoding='utf-8') as f:
    f.write('cat')
with open('note.txt', encoding='utf-8') as f:
    first = f.read()
    second = f.read()
print(repr(first))
print(repr(second))

Answer

'cat'
''

Question 23

with open('note.txt', 'w', encoding='utf-8') as f:
    f.write('old text')
with open('note.txt', 'w', encoding='utf-8') as f:
    f.write('new')
with open('note.txt', encoding='utf-8') as f:
    print(f.read())

Answer

new

Question 24

with open('words.txt', 'w', encoding='utf-8') as f:
    f.write('sun')
    f.write('rise')
with open('words.txt', encoding='utf-8') as f:
    print(f.read())

Answer

sunrise

Question 25

with open('poem.txt', 'w', encoding='utf-8') as f:
    f.write('cat\nmat\n')
with open('poem.txt', encoding='utf-8') as f:
    for line in f:
        print(repr(line))

Answer

'cat\n'
'mat\n'

Short Markdown Examples

These two examples combine find and slicing from the reading. The supplied strings have one matching pair of markers. Trace the positions and the slice before writing the output.

Question 26

line = 'one *two* three'
start = line.find('*')
end = line.find('*', start + 1)
print(line[start + 1:end])

Answer

two

Question 27

def compile_bold(line):
    start = line.find('**')
    end = line.find('**', start + 2)
    return line[:start] + '<b>' + line[start + 2:end] + '</b>' + line[end + 2:]

print(compile_bold('one **two** three'))

Answer

one <b>two</b> three

Markdown Tracing Challenges

These longer functions prepare you for the Markdown compiler project. They include correct and incorrect implementations. First trace a matching pair of markers, then check what happens to an unmatched marker. For the loops, keep track of i, end, and result after each iteration. Compare related versions: a small change can preserve, remove, or stop processing the remaining text.

Question 28

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            if i + 1 < len(line) and '*' in line[i+1:]:
                end = line.find('*', i+1)
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                result += '*'
                i += 1
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta* gamma *delta')
print(result)

Answer

alpha <i>beta</i> gamma *delta

Question 29

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i = len(line)
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta* gamma *delta')
print(result)

Answer

alpha <i>beta</i> gamma

Question 30

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i = len(line)
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta* gamma *delta*')
print(result)

Answer

alpha <i>beta</i> gamma <i>delta</i>

Question 31

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i = len(line)
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta gamma delta')
print(result)

Answer

alpha

Question 32

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i += 1
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta* gamma *delta')
print(result)

Answer

alpha <i>beta</i> gamma delta

Question 33

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i += 1
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta gamma delta')
print(result)

Answer

alpha beta gamma delta

Question 34

def compile_italic_star(line):
    result = ''
    i = 0
    while i < len(line):
        if line[i] == '*':
            end = line.find('*', i+1)
            if end != -1:
                result += '<i>' + line[i+1:end] + '</i>'
                i = end + 1
            else:
                i += 1
        else:
            result += line[i]
            i += 1
    return result
result = compile_italic_star('alpha *beta gamma delta*')
print(result)

Answer

alpha <i>beta gamma delta</i>

Question 35

def compile_bold_stars(line):
    start = line.find('**')
    if start == -1 or len(line) < 4:
        return line

    end = line[start + 2:].find('**')
    if end == -1:
        return line

    end = end + start + 2
    return line[:start] + '<b>' + line[start + 2:end] + '</b>' + line[end + 2:]
result = compile_bold_stars('alpha **beta** gamma **delta**')
print(result)

Answer

alpha <b>beta</b> gamma **delta**

Question 36

def compile_bold_stars(line):
    start = line.find('**')
    if start == -1 or len(line) < 4:
        return line

    end = line[start + 2:].find('**')
    if end == -1:
        return line

    end = end + start + 2
    return line[:start] + '<b>' + line[start + 2:end] + '</b>' + line[end + 2:]
result = compile_bold_stars('alpha **beta** gamma **delta')
print(result)

Answer

alpha <b>beta</b> gamma **delta

Question 37

def compile_bold_stars(line):
    start = line.find('**')
    if start == -1 or len(line) < 4:
        return line

    end = line[start + 2:].find('**')
    if end == -1:
        return line

    end = end + start + 2
    return line[:start] + '<b>' + line[start + 2:end] + '</b>' + line[end + 2:]
result = compile_bold_stars('alpha beta gamma **delta')
print(result)

Answer

alpha beta gamma **delta