Week 6
Solutions to File I/O and Consolidatio

Exercise 1 - Basic File I/O

Here we create a file, and add some random lines to it. Then we read and print out the file contents.
week6_solutions_ex1.py
# create a file
my_file = open("musings.txt", "w+")
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# write some things to the file
my_file.write("These are some of my thoughts\n")
my_file.write("The solutions are so great\n")
my_file.write("Thanks for these interesting exercises alex\n")
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# close the file, so that we can then read from it
my_file.close()
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# open the file for reading
my_file = open("musings.txt", "r")
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# now read each line in the file, and print it out
for line in my_file:
print(line)
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# close access to the file again
my_file.close()

Exercise 2 - Wherefore art thou paragraph

Here we define a function to read N paragraphs from a file, and print them.
week6_solutions_ex2.py
def read_shakespeare(num_of_paragraphs):
# open the file, read all the lines and store them
shakespeare_file = open("shakespeare.txt", "r")
lines = shakespeare_file.readlines()
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current_paragraph = 1
line_num = 0
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# keep printing, until we are at the paragraph we want to stop at
while current_paragraph <= num_of_paragraphs:
current_line = lines[line_num]
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# remove whitespace from line, as paragraph lines have spaces before
# the number, check if its the next paragraph
if current_line.strip() == str(current_paragraph + 1):
# we have reached the next paragraph
current_paragraph = current_paragraph + 1
if current_paragraph > num_of_paragraphs:
break # don't print the line if we exceed paragraph
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# print the line, rstrip removes newline character at the end of the line
print(lines[line_num].rstrip())
line_num = line_num + 1
​
read_shakespeare(3)

Exercise 3 - Caesar's Cipher Consolidates Cool Class

week6_solutions_ex3.py
def decipher(file_name, decode_word, frequency):
cipher_file = open(file_name, "r")
cipher = cipher_file.readline()
cipher_offset = 0
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decode_diff = []
for index in range(len(decode_word) - 1):
ascii_diff = ord(decode_word[index+1]) - ord(decode_word[index])
if(ascii_diff < 0):
ascii_diff = ascii_diff % 26
decode_diff.append(ascii_diff)
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words = cipher.split(" ")
word_count = {}
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# print(decode_diff)
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for word in words:
if len(word) == len(decode_word) and word in word_count:
word_count[word] = word_count[word] + 1
elif len(word) == len(decode_word):
word_count[word] = 1
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# print(word_count)
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for key in word_count:
if word_count[key] == frequency:
# now check letter positions
correct_positions = True
for index in range(len(key)-1):
# check ascii position changes between key and decode_word
ascii_diff = ord(key[index+1]) - ord(key[index])
if(ascii_diff < 0):
ascii_diff = ascii_diff % 26
correct_positions = correct_positions & (ascii_diff == decode_diff[index])
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# we have found the word
if correct_positions:
print("here")
cipher_offset = ord(decode_word[0]) - ord(key[0])
if cipher_offset < 0:
cipher_offset = cipher_offset % 26
break
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decryted_words = []
for word in words:
new_word = ""
for char in word:
new_char = chr(97 + ((ord(char) - 97 + cipher_offset) % 26))
new_word = new_word + new_char
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decryted_words.append(new_word)
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plaintext = " ".join(decryted_words)
print(plaintext)
​
decipher("mary.txt", 'the', 4)
decipher("charles.txt", 'of', 12)
decipher("agatha.txt", 'train', 2)
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On this page
Exercise 1 - Basic File I/O
Exercise 2 - Wherefore art thou paragraph
Exercise 3 - Caesar's Cipher Consolidates Cool Class