Answer to Question #246608 in Python for Raymond Ekwubiri

Question

. Consider the loop from Section 8.3 of your textbook.

prefixes = 'JKLMNOPQ'
suffix = 'ack'

for letter in prefixes:
print(letter + suffix)

Put this code into a Python script and run it. Notice that it prints the names "Oack" and "Qack".

Modify the program so that it prints "Ouack" and "Quack" but leaves the other names the same.

Include the modified Python code and the output in your submission.

2. Give at least three examples that show different features of string slices. Describe the feature illustrated by each example. Invent your own examples. Do not copy them for the textbook or any other source.

Answer 1

# names.py
# Modify the program so that it prints "Ouack" and "Quack" but leaves the other
# names the same.

prefixes = 'JKLMNOPQ'
suffix = 'ack'
for ​letter in prefixes:
    # for letter in prefixes:
    #     print(letter + suffix)
    if letter not in 'OQ':
        print(letter + suffix)
    else:
        print(letter + 'u' + suffix

output.txt

Jack
Kack
Lack
Mack
Nack
Ouack
Pack
Quack

2.examples.py

# Give at least three examples that show diferent features of string slices.

print('Example 1: Substrings and every i-th character')
string ​= 'Describe the feature illustrated by each example.'
strA = string[0:9]
strB = string[9::2]
strC = string[10::2]
listD = [x + y for x, y in zip(strB, strC)]
string2 = strA + ''.join(listD)
print(string2)
assert string2 == string
print('')

print('Example 2: Ranges and slices and slice objects')
# docs.python.org/3/library/functions.html#slice
nums = list(range(1,10))
nums2 = nums[:-1:2] + [nums[-1]] + nums[1::2] + nums[50:100:3]
nums3 = list(range(1,10,2)) + list(range(2,10,2))
print(nums2)
print(nums3)
assert nums2 == nums3
string ​= 'Describe the feature illustrated by each example.'
string2 = string[:-1:2] + string[-1] + string[1::2] + string[50:100:3]
lstA = [string[i] for i in range(0,len(string),2)]
# lstB = [string[i] for i in range(1,len(string),2)]  # what a mess
# lstB = string[slice(1,len(string),2)]  # string, not a list :)
lstB = list(string)[slice(1,len(string),2)]
lstC = [string[i] for i in range(50,100,3) if i in range(len(string))]
string3 = ''.join(lstA) + ''.join(lstB) + ''.join(lstC)
print(string2)
print(string3)
assert string2 == string3
print('')

print('Example 3: Copying and reversing')
string ​= 'Describe the feature illustrated by each example.'
string2 = string[:]
try: string2[-1] = '!'
except TypeError as e: print(e)
string3 = string
try: string3[-1] = '!'
except TypeError as e: print(e)
string ​= ''.join(reversed(string))  # it's slower then slicing
string2 = string2[::-1]
print(string)
print(string2)
print(string3)
assert string2 == string
print