1
00:00:00,210 --> 00:00:08,400
So the Getler function, which we have defined here, is basically text messages, string and returns

2
00:00:08,400 --> 00:00:16,680
a dictionary value whose keys are a single uppercase letter strings and whose values are in BIJA that

3
00:00:16,680 --> 00:00:21,150
stores the number of times that letter goes in the message parameter.

4
00:00:21,510 --> 00:00:29,160
So here we have created a letter found SDR variable by assigning it to a dictionary that has all said

5
00:00:29,200 --> 00:00:31,400
Stewart, initial value of zero.

6
00:00:31,430 --> 00:00:34,080
Hence we have set all the keys from A to Z.

7
00:00:34,290 --> 00:00:36,060
Everything's A to Z.

8
00:00:36,500 --> 00:00:43,680
OK, we then increment the value associated with the key until they represent the count of each letter

9
00:00:43,680 --> 00:00:47,460
by taking each character in the message using a form Lupul.

10
00:00:47,850 --> 00:00:52,120
So we have before this year in the message dot Apple.

11
00:00:52,530 --> 00:00:56,790
If your letter Asgeir is in the constant then you make or incremental value.

12
00:00:57,300 --> 00:01:04,380
So therefore loop iterate through each character in the uppercase version of the message SDR and assigns

13
00:01:04,380 --> 00:01:07,190
the character to the letter OCR variable.

14
00:01:07,560 --> 00:01:14,310
Then we check whether the character exists in the constant letters string because we don't want to count

15
00:01:14,310 --> 00:01:16,420
the known little characters in the messages.

16
00:01:16,980 --> 00:01:23,280
So when the letter is a part of your constant increments, the value at letter count are the index of

17
00:01:23,280 --> 00:01:25,680
letters plus is equal to one.

18
00:01:25,710 --> 00:01:32,970
So after the for loop, the letter count is your dictionary should have a count showing how often each

19
00:01:32,970 --> 00:01:40,080
letter appeared in the messages and the dictionary is written from the get a letter count as saying

20
00:01:40,080 --> 00:01:42,120
return the letter count as dear.

21
00:01:43,020 --> 00:01:51,600
OK, now if we move on to the next one, say getting the first member of the stupid now the get item

22
00:01:51,600 --> 00:01:58,360
at the index zero function returns the items at index zero when the duopolies pass to it.

23
00:01:58,590 --> 00:02:01,640
So it is just having a simple written statement given.

24
00:02:01,680 --> 00:02:07,680
And later in this session we will pass this function to this sort method to sort the frequency of the

25
00:02:07,680 --> 00:02:09,390
letters into numerical order.

26
00:02:09,810 --> 00:02:14,550
OK, we will look at this in detail in the some other sections of hacking.

27
00:02:14,820 --> 00:02:18,480
But as of now, currently, we will be using this function to sort.

28
00:02:19,110 --> 00:02:23,190
So moving to the ordering the letters in the message by frequency.

29
00:02:23,490 --> 00:02:30,420
The next function that we have defined is our get frequency order function, which takes a message string

30
00:02:30,420 --> 00:02:37,080
as an argument and returns a string with a twenty six uppercase letters of alphabet arranged by how

31
00:02:37,080 --> 00:02:43,100
frequently the upbuilding message parameter f message is readable English instead of random anything.

32
00:02:43,350 --> 00:02:49,650
It's likely that the string will be similar, if not identical to the string in the edit or in constant.

33
00:02:50,130 --> 00:02:56,250
The code in the frequency or the function does most of the work of calculating the string frequency

34
00:02:56,540 --> 00:03:01,860
score, which we will be using in order which will be used in the Virginia hacking program in the next

35
00:03:01,860 --> 00:03:02,370
session.

36
00:03:02,400 --> 00:03:07,980
OK, for example, if we have passed certain string to it, the function would return the string in

37
00:03:07,980 --> 00:03:13,920
a particular order because E is the most common letter which would be used, for example, followed

38
00:03:13,920 --> 00:03:16,360
by B then I then and then so on.

39
00:03:16,860 --> 00:03:20,490
So the frequency of the function consists of five steps.

40
00:03:20,790 --> 00:03:27,270
First, if you are counting the letters in the string, second is creating a dictionary of frequency

41
00:03:27,270 --> 00:03:35,220
columns and the letter list is sorting the letters list in the rebels or in order for this converting

42
00:03:35,220 --> 00:03:37,260
this data to the list of tuples.

43
00:03:37,260 --> 00:03:42,900
And the last is converting the list into the final string to return from the function, get frequency

44
00:03:42,900 --> 00:03:43,650
or the function.

45
00:03:43,770 --> 00:03:49,740
Now let us look at each of these step into succumbing to the first one that is found in the letters

46
00:03:49,740 --> 00:03:51,900
with the little count function.

47
00:03:52,320 --> 00:03:58,380
OK, so over here before step off your get frequency auto function, which calls together that account

48
00:03:58,380 --> 00:04:06,270
function with the message parameter to get the dictionary named letter frequency is containing count

49
00:04:06,270 --> 00:04:08,830
of every letter in the message.

50
00:04:09,450 --> 00:04:16,140
OK, so after this two lines of code that we have written, we get the values there and then we pass

51
00:04:16,140 --> 00:04:18,180
this particular string as the parameter.

52
00:04:18,180 --> 00:04:24,060
For example, say we have passed by and hacking something like that or Alan Matheson.

53
00:04:25,350 --> 00:04:30,870
Now this particular string would be then assigned to the letter to frequency function and then we will

54
00:04:30,870 --> 00:04:35,040
get how much it is being used or how frequently it is being used.

55
00:04:35,070 --> 00:04:41,270
OK, then next we have is creating a dictionary of frequently counts and the letter list.

56
00:04:41,280 --> 00:04:45,510
So the second step in this is all this function is to create a dictionary.

57
00:04:45,810 --> 00:04:52,260
That is the frequency to let Oresteia, whose keys are the frequency count and whose values are the

58
00:04:52,260 --> 00:04:59,340
list of letters with those frequency counts, whereas the letter to frequency ACR, which is a.

59
00:04:59,750 --> 00:05:07,960
Redmap Lecoq used to frequency values the frequency to let Orestiada, which we have that Maxey frequency

60
00:05:07,960 --> 00:05:15,430
keys to the list of the letter values, so we will need to flip the key and the values in later to frequency

61
00:05:15,430 --> 00:05:21,580
dictionary will flip the keys and values because the multiple letters would have the same frequency

62
00:05:21,580 --> 00:05:23,170
count be N.W..

63
00:05:23,170 --> 00:05:29,380
Both would have a frequency count, for example, Silvani to put them in a dictionary, said 30 Colombe.

64
00:05:29,380 --> 00:05:36,010
And because the order dictionary key must be unique, otherwise dictionary values will look like something

65
00:05:36,010 --> 00:05:41,950
like 30 Colombe another 30 colon w which is wrong, which will simply overwrite one of these key value

66
00:05:41,950 --> 00:05:42,900
pair with another.

67
00:05:43,060 --> 00:05:48,760
So to make the frequency to little dictionary, we have created a blank dictionary first over here.

68
00:05:48,760 --> 00:05:51,550
That is your frequency to letter estab.

69
00:05:51,880 --> 00:05:56,740
Then we have a for loop saying four letters are in your constant letters this year.

70
00:05:56,890 --> 00:06:04,270
If the frequency is still at the index letter is not in your frequency to let Oresteia then we are saying

71
00:06:04,570 --> 00:06:08,050
frequency two letter instead of the index of letter to frequency.

72
00:06:08,050 --> 00:06:15,130
Asgeir letter instead is equal to last year is we are saying frequency two letters are the index of

73
00:06:15,130 --> 00:06:18,640
negative frequency StarTalk upending the value of letters.

74
00:06:19,060 --> 00:06:25,960
So in this particular loop we are looping over all the letters and letters and then the if statement

75
00:06:25,960 --> 00:06:33,850
checks whether the letter frequencies or the frequency are already exist as a the frequency two letters.

76
00:06:34,420 --> 00:06:36,430
If not, then it adds this.

77
00:06:36,430 --> 00:06:39,040
Give the list of letters as the value.

78
00:06:39,130 --> 00:06:45,820
And if the letters frequency already exist and the key in the frequency to letters, it simply updates

79
00:06:45,820 --> 00:06:47,920
the letter to the end of the list.

80
00:06:48,010 --> 00:06:50,970
Already in the letter to frequency and stamp.

81
00:06:51,280 --> 00:06:57,970
Now using the example value of the letter, the frequency are created using some particular string.

82
00:06:58,330 --> 00:07:03,910
The frequency two letters should now return something which will have like although we had everything

83
00:07:03,910 --> 00:07:06,660
to zero, but now we will have a control, key value.

84
00:07:06,670 --> 00:07:13,330
But now if we move on to the next thing that this sorting the letter list in reverse order.

85
00:07:13,480 --> 00:07:21,370
Now the third step in this get frequency involves sorting the letter strings in each list of frequency.

86
00:07:21,370 --> 00:07:22,420
Two letters, dear.

87
00:07:22,720 --> 00:07:28,600
So we recall that the frequency two letters are evaluates to a list of letters that has a frequency

88
00:07:28,600 --> 00:07:29,770
count of frequency.

89
00:07:30,040 --> 00:07:35,140
We will use a list because it's possible for two or more letters to have the same frequency count,

90
00:07:35,140 --> 00:07:40,080
in which case it would list would have strings made up of two or more letters.

91
00:07:40,270 --> 00:07:45,130
So when multiple letters have the same frequency commas, we want to sort that letters in the reverse

92
00:07:45,130 --> 00:07:49,150
order compared to the order in which they appear in the old string.