Related
I am writing a program to decrypt a message and only given assumption that the maximum occur letter of decrypted message is "e". No shift number is given. Below code are my workdone. I can only hardcode the shift number to decrypt the given message, but if the message changed my code of course didn't work.
from collections import Counter
import string
message = "Zyp cpxpxmpc ez wzzv fa le esp delcd lyo yze ozhy le jzfc qppe Ehz ypgpc rtgp fa hzcv Hzcv rtgpd jzf xplytyr lyo afcazdp lyo wtqp td pxaej hteszfe te Escpp tq jzf lcp wfnvj pyzfrs ez qtyo wzgp cpxpxmpc te td espcp lyo ozye esczh te lhlj Depaspy Slhvtyr"
#frequency of each letter
letter_counts = Counter(message)
print(letter_counts) # Print the count of each element in string
#find max letter
maxFreq = -1
maxLetter = None
letter_counts[' '] = 0 # Don't count spaces zero count
for letter, freq in letter_counts.items():
print(letter, ":", freq)
maxLetter = max(letter_counts, key = letter_counts.get) # Find max freq letter in the string
print("Max Ocurring Letter:", maxLetter)
#right shift for encrypting and left shift for descripting.
#predict shift
#assume max letter is 'e'
letters = string.ascii_letters #contains 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
shift = 15 #COMPUTE SHIFT HERE (hardcode)
print("Predicted Shift:", shift)
totalLetters = 26
keys = {} #use dictionary for letter mapping
invkeys = {} #use dictionary for inverse letter mapping, you could use inverse search from original dict
for index, letter in enumerate(letters):
# cypher setup
if index < totalLetters: #lowercase
# Dictionary for encryption
letter = letters[index]
keys[letter] = letters[(index + shift) % 26]
# Dictionary for decryption
invkeys = {val: key for key, val in keys.items()}
else: #uppercase
# Dictionary for encryption
keys[letter] = letters[(index + shift) % 26 + 26]
# Dictionary for decryption
invkeys = {val: key for key, val in keys.items()}
print("Cypher Dict", keys)
#decrypt
decryptedMessage = []
for letter in message:
if letter == ' ': #spaces
decryptedMessage.append(letter)
else:
decryptedMessage.append(keys[letter])
print("Decrypted Message:", ''.join(decryptedMessage)) #join is used to put list inot string
# Checking if message is the same as the encrypt message provided
#Encrypt
encryptedMessage = []
for letter in decryptedMessage:
if letter == ' ': #spaces
encryptedMessage.append(letter)
else:
encryptedMessage.append(invkeys[letter])
print("Encrypted Message:", ''.join(encryptedMessage)) #join is used to put list inot string
The encrypt part of code is not necessary to exist, it is for checking only. It would be great if someone could help to modify my code/ give me some hints for the predict shift part. Thanks!
Output of the code:
Cypher Dict {'a': 'p', 'b': 'q', 'c': 'r', 'd': 's', 'e': 't', 'f': 'u', 'g': 'v', 'h': 'w', 'i': 'x', 'j': 'y', 'k': 'z', 'l': 'a', 'm': 'b', 'n': 'c', 'o': 'd', 'p': 'e', 'q': 'f', 'r': 'g', 's': 'h', 't': 'i', 'u': 'j', 'v': 'k', 'w': 'l', 'x': 'm', 'y': 'n', 'z': 'o', 'A': 'P', 'B': 'Q', 'C': 'R', 'D': 'S', 'E': 'T', 'F': 'U', 'G': 'V', 'H': 'W', 'I': 'X', 'J': 'Y', 'K': 'Z', 'L': 'A', 'M': 'B', 'N': 'C', 'O': 'D', 'P': 'E', 'Q': 'F', 'R': 'G', 'S': 'H', 'T': 'I', 'U': 'J', 'V': 'K', 'W': 'L', 'X': 'M', 'Y': 'N', 'Z': 'O'}
Decrypted Message: One remember to look up at the stars and not down at your feet Two never give up work Work gives you meaning and purpose and life is empty without it Three if you are lucky enough to find love remember it is there and dont throw it away Stephen Hawking
Encrypted Message: Zyp cpxpxmpc ez wzzv fa le esp delcd lyo yze ozhy le jzfc qppe Ehz ypgpc rtgp fa hzcv Hzcv rtgpd jzf xplytyr lyo afcazdp lyo wtqp td pxaej hteszfe te Escpp tq jzf lcp wfnvj pyzfrs ez qtyo wzgp cpxpxmpc te td espcp lyo ozye esczh te lhlj Depaspy Slhvtyr
This has three components:
Finding the character with max frequency:
test_str = "" # your string
counter = Counter(test_str)
keys = sorted(counter, key=counter.get, reverse=True)
res = keys[1] if keys[0] == " " else keys[0]
Calculating the shift:
shift = ord('e') - ord(res)
Encrypting/decrypting the string, which is trivial since you know the shift now
Something like this should allow you to calculate the shift based on the assumption that the letter in the original message with the highest frequency is 'e':
letter_counts = Counter(message)
e_encrypted = [k for k, v in letter_counts.items() if v == max(count for c, count in letter_counts.items() if c != ' ')][0]
shift = (ord('e') - ord(e_encrypted)) % 26
Or, to unroll the comprehensions for ease of understanding:
letter_counts = Counter(message)
e_encrypted, max_v = None, 0
for k, v in letter_counts.items():
if v > max_v and k != ' ':
e_encrypted, max_v = k, v
shift = (ord('e') - ord(e_encrypted)) % 26
It does the following:
take frequency counts of characters in message using the Counter class
find the maximum frequency, and the character with that maximum frequency
set the shift equal to the difference between the ascii value of that character and the letter 'e' (modulo 26)
I hope you are doing well. I'm working on a dictionary program:
strEntry = str(input("Enter a string: ").upper())
strEntry = strEntry.replace(",", "")
strEntry = strEntry.replace(" ", "")
print('')
def freq_finder(strFinder):
dict = {}
for i in strFinder:
keys = dict.keys()
if i in keys:
dict[i] += 1
else:
dict[i] = 1
return dict
newDic = freq_finder(strEntry)
print(newDic)
newLetter = str(input("Choose a letter: ").upper())
if newLetter in newDic.values():
print("Number of occurrence of", message.count(newLetter))
newDic.pop(newLetter)
print("Dictinary after that letter removed:", newDic)
else:
print("Letter not in dictionary")
sortedDic = sorted(newDic)
print(sortedDic)
Everything works fine before this part:
newLetter = str(input("Choose a letter: ").upper())
if newLetter in newDic.values():
print("Number of occurrence of", message.count(newLetter))
newDic.pop(newLetter)
print("Dictinary after that letter removed:", newDic)
else:
print("Letter not in dictionary")
I'm trying to figure out how to check whether the letter is in the dictionary. If it is not, display the message “Letter not in dictionary”. Otherwise, display the frequency count of that letter, remove the letter from the dictionary and display the dictionary after that letter has been removed.
It should look something like this:
Enter a string: Magee, Mississippi
Dictionary: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'S': 4, 'P': 2}
Choose a letter: s
Frequency count of that letter: 4
Dictionary after that letter removed: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'P': 2}
Letters sorted: ['A', 'E', 'G', 'I', 'M', 'P']
I would highly appreciate it if you could tell me what's wrong and how to fix it.
Check for the keys, not the value (Because the Value is a number, not a letter) -
if newLetter in newDic: # Or if newLetter in list(newDic.keys())
print("Number of occurrence of", message.count(newLetter))
For this - Dictionary: {'M': 2, 'A': 1, 'G': 1, 'E': 2, 'I': 4, 'S': 4, 'P': 2}, you could use Collections.Counter instead
I am very new to python and trying to find the solution to this for a class.
I need the function missing_letters to take a list, check the letters using histogram and then loop over the letters in alphabet to determine which are missing from the input parameter. Finally I need to print the letters that are missing, in a string.
alphabet = "abcdefghijklmnopqrstuvwxyz"
test = ["one","two","three"]
def histogram(s):
d = dict()
for c in s:
if c not in d:
d[c] = 1
else:
d[c] += 1
return d
def missing_letter(s):
for i in s:
checked = (histogram(i))
As you can see I haven't gotten very far, at the moment missing_letters returns
{'o': 1, 'n': 1, 'e': 1}
{'t': 1, 'w': 1, 'o': 1}
{'t': 1, 'h': 1, 'r': 1, 'e': 2}
I now need to loop over alphabet to check which characters are missing and print. Any help and direction will be much appreciated. Many thanks!
You can use set functions in python, which is very fast and efficient:
alphabet = set('abcdefghijklmnopqrstuvwxyz')
s1 = 'one'
s2 = 'two'
s3 = 'three'
list_of_missing_letters = set(alphabet) - set(s1) - set(s2) - set(s3)
print(list_of_missing_letters)
Or like this:
from functools import reduce
alphabet = set('abcdefghijklmnopqrstuvwxyz')
list_of_strings = ['one', 'two', 'three']
list_of_missing_letters = set(alphabet) - \
reduce(lambda x, y: set(x).union(set(y)), list_of_strings)
print(list_of_missing_letters)
Or using your own histogram function:
alphabet = "abcdefghijklmnopqrstuvwxyz"
test = ["one", "two", "three"]
def histogram(s):
d = dict()
for c in s:
if c not in d:
d[c] = 1
else:
d[c] += 1
return d
def missing_letter(t):
test_string = ''.join(t)
result = []
for l in alphabet:
if l not in histogram(test_string).keys():
result.append(l)
return result
print(missing_letter(test))
Output:
['a', 'b', 'c', 'd', 'f', 'g', 'i', 'j', 'k', 'l', 'm', 'p', 'q', 's', 'u', 'v', 'x', 'y', 'z']
from string import ascii_lowercase
words = ["one","two","three"]
letters = [l.lower() for w in words for l in w]
# all letters not in alphabet
letter_str = "".join(x for x in ascii_lowercase if x not in letters)
Output:
'abcdfgijklmpqsuvxyz'
It is not the easiest question to understand, but from what I can gather you require all the letters of the alphabet not in the input to be returned in console.
So a loop as opposed to functions which have been already shown would be:
def output():
output = ""
for i in list(alphabet):
for key in checked.keys():
if i != key:
if i not in list(output):
output += i
print(output)
Sidenote: Please either make checked a global variable or put it outside of function so this function can use it
I'm trying to create a Python function that uses the Caesar cipher to encrypt a message.
So far, the code I have is
letter = input("Enter a letter: ")
def alphabet_position(letter):
alphabet_pos = {'A':0, 'a':0, 'B':1, 'b':1, 'C':2, 'c':2, 'D':3,
'd':3, 'E':4, 'e':4, 'F':5, 'f':5, 'G':6, 'g':6,
'H':7, 'h':7, 'I':8, 'i':8, 'J':9, 'j':9, 'K':10,
'k':10, 'L':11, 'l':11, 'M':12, 'm':12, 'N': 13,
'n':13, 'O':14, 'o':14, 'P':15, 'p':15, 'Q':16,
'q':16, 'R':17, 'r':17, 'S':18, 's':18, 'T':19,
't':19, 'U':20, 'u':20, 'V':21, 'v':21, 'W':22,
'w':22, 'X':23, 'x':23, 'Y':24, 'y':24, 'Z':25, 'z':25 }
pos = alphabet_pos[letter]
return pos
When I try to run my code, it will ask for the letter but it doesn't return anything after that
Please help if you have any suggestions.
you would need to access your dictionary in a different way:
pos = alphabet_pos.get(letter)
return pos
and then you can finally call the function.
alphabet_position(letter)
You can define two dictionaries, one the reverse of the other. You need to be careful on a few aspects:
Whether case is important. If it's not, use str.casefold as below.
What happens when you roll off the end of the alphabet, e.g. 13th letter after "z". Below we assume you start from the beginning again.
Don't type out the alphabet manually. You can use the string module.
Here's a demo:
letter = input("Enter a letter: ")
from string import ascii_lowercase
def get_next(letter, n):
pos_alpha = dict(enumerate(ascii_lowercase))
alpha_pos = {v: k for k, v in pos_alpha.items()}
return pos_alpha[alpha_pos[letter.casefold()] + n % 26]
get_next(letter, 13)
Enter a letter: a
'n'
If you need a entirely new encoded dict
import string
import numpy as np, random
letters = string.ascii_uppercase
d=dict(zip(list(letters),range(0,len(letters))))
encoded_dic={}
def get_caesar_value(v, by=13):
return(v+by)%26
for k,v in d.items():
encoded_dic[k]=chr(65+get_caesar_value(v))
print(encoded_dic)
Output:
{'A': 'N', 'C': 'P', 'B': 'O', 'E': 'R', 'D': 'Q', 'G': 'T', 'F': 'S', 'I': 'V', 'H': 'U', 'K': 'X', 'J': 'W', 'M': 'Z', 'L': 'Y', 'O': 'B', 'N': 'A', 'Q': 'D', 'P': 'C', 'S': 'F', 'R': 'E', 'U': 'H', 'T': 'G', 'W': 'J', 'V': 'I', 'Y': 'L', 'X': 'K', 'Z': 'M'}
The code you have only maps letters to a position. We'll rewrite it and make a rotate function.
Code
import string
import itertools as it
LOOKUP = {
**{x:i for i, x in enumerate(string.ascii_lowercase)},
**{x:i for i, x in enumerate(string.ascii_uppercase)}
}
def abc_position(letter):
"""Return the alpha position of a letter."""
return LOOKUP[letter]
def rotate(letter, shift=13):
"""Return a letter shifted some positions to the right; recycle at the end."""
iterable = it.cycle(string.ascii_lowercase)
start = it.dropwhile(lambda x: x != letter.casefold(), iterable)
# Advance the iterator
for i, x in zip(range(shift+1), start):
res = x
if letter.isupper():
return res.upper()
return res
Tests
func = abc_position
assert func("a") == 0
assert func("A") == 0
assert func("c") == 2
assert func("z") == 25
func = rotate
assert func("h") == "u"
assert func("a", 0) == "a"
assert func("A", 0) == "A"
assert func("a", 2) == "c"
assert func("c", 3) == "f"
assert func("A", 2) == "C"
assert func("a", 26) == "a"
# Restart after "z"
assert func("z", 1) == "a"
assert func("Z", 1) == "A"
Demo
>>> letter = input("Enter a letter: ")
Enter a letter: h
>>> rot = rotate(letter, 13)
>>> rot
'u'
>>> abc_position(rot)
20
Here we rotated the letter "h" 13 positions, got a letter and then determined the position of this resultant letter in the normal string of abc's.
Details
abc_position()
This function was rewritten to lookup the position of a letter. It merges two dictionaries:
one that enumerates a lowercase ascii letters
one that enumerates a uppercase ascii letters
The string module has this letters already.
rotate()
This function only rotates lowercase letters; uppercase letters are translated from the lowercase position. The string of letters is rotated by making an infinite cycle (an iterator) of lowercase letters.
The cycle is first advanced to start at the desired letter. This is done by dropping all letters that don't look like the one passed in.
Then it is advanced in a loop some number of times equal to shift. The loop is just one way to consume or move the iterator ahead. We only care about the last letter, not the ones in between. This letter is returned, either lower or uppercase.
Since a letter is returned (not a position), you can now use your abc_position() function to find it's normal position.
Alternatives
Other rotation functions can substitute rotate():
import codecs
def rot13(letter):
return codecs.encode(letter, "rot13")
def rot13(letter):
table = str.maketrans(
"ABCDEFGHIJKLMabcdefghijklmNOPQRSTUVWXYZnopqrstuvwxyz",
"NOPQRSTUVWXYZnopqrstuvwxyzABCDEFGHIJKLMabcdefghijklm")
return str.translate(letter, table)
However, these options are constrained to rot13, while rotate() can be shifted by any number. Note: rot26 will cycle back to the beginning, e.g. rotate("a", 26) -> a.
See also this post on how to make true rot13 cipher.
See also docs on itertools.cycle and itertools.dropwhile.
You can do it with quick calculations from ord and chr functions instead:
def encrypt(letter):
return chr((ord(letter.lower()) - ord('a') + 13) % 26 + ord('a'))
so that:
print(encrypt('a'))
print(encrypt('o'))
outputs:
n
b
I have a list that contains dictionaries with Letters and Frequencies. Basically, I have 53 dictionaries each for every alphabet (lowercase and uppercase) and space.
adict = {'Letter':'a', 'Frequency':0}
bdict = {'Letter':'b', 'Frequency':0}
cdict = {'Letter':'c', 'Frequency':0}
If you input a word, it will scan the word and update the frequency for its corresponding letter.
for ex in range(0, len(temp)):
if temp[count] == 'a': adict['Frequency']+=1
elif temp[count] == 'b': bdict['Frequency']+=1
elif temp[count] == 'c': cdict['Frequency']+=1
For example, I enter the word "Hello", The letters H,e,l,l,o is detected and its frequencies updated. Non zero frequencies will be transferred to a new list.
if adict['Frequency'] != 0 : newArr.append(adict)
if bdict['Frequency'] != 0 : newArr.append(bdict)
if cdict['Frequency'] != 0 : newArr.append(cdict)
After this, I had the newArr sorted by Frequency and transferred to a new list called finalArr. Below is a sample list contents for the word "Hello"
{'Letter': 'H', 'Frequency': 1}
{'Letter': 'e', 'Frequency': 1}
{'Letter': 'o', 'Frequency': 1}
{'Letter': 'l', 'Frequency': 2}
Now what I want is to transfer only the key values to 2 seperate lists; letterArr and numArr. How do I do this? my desired output is:
letterArr = [H,e,o,l]
numArr = [1,1,1,2]
Why don't you just use a collections.Counter? For example:
from collections import Counter
from operator import itemgetter
word = input('Enter a word: ')
c = Counter(word)
letter_arr, num_arr = zip(*sorted(c.items(), key=itemgetter(1,0)))
print(letter_arr)
print(num_arr)
Note the use of sorted() to sort by increasing frequency. itemgetter() is used to reverse the sort order so that the sort is performed first on the frequency, and then on the letter. The sorted frequencies are then separated using zip() on the unpacked list.
Demo
Enter a word: Hello
('H', 'e', 'o', 'l')
(1, 1, 1, 2)
The results are tuples, but you can convert to lists if you want with list(letter_arr) and list(num_arr).
I have a hard time understanding your data structure choice for this problem.
Why don't you just go with a dictionary like this:
frequencies = { 'H': 1, 'e': 1, 'l': 2, 'o': 1 }
Which is even easier to implement with a Counter:
from collections import Counter
frequencies = Counter("Hello")
print(frequencies)
>>> Counter({ 'H': 1, 'e': 1, 'l': 2, 'o': 1 })
Then to add another word, you'd simply have to use the updatemethod:
frequencies.update("How")
print(frequencies)
>>> Counter({'l': 2, 'H': 2, 'o': 2, 'w': 1, 'e': 1})
Finally, to get your 2 arrays, you can do:
letterArr, numArr = zip(*frequencies.items())
This will give you tuples though, if you really need lists, just do: list(letterArr)
You wanted a simple answer without further todo like zip, collections, itemgetter etc. This does the minimum to get it done, 3 lines in a loop.
finalArr= [{'Letter': 'H', 'Frequency': 1},
{'Letter': 'e', 'Frequency': 1},
{'Letter': 'o', 'Frequency': 1},
{'Letter': 'l', 'Frequency': 2}]
letterArr = []
numArr = []
for i in range(len(finalArr)):
letterArr.append(finalArr[i]['Letter'])
numArr.append(finalArr[i]['Frequency'])
print letterArr
print numArr
Output is
['H', 'e', 'o', 'l']
[1, 1, 1, 2]