WEBVTT

1
00:00:02.240 --> 00:00:04.620
Okay.
So it's time for a Python challenge.

2
00:00:04.620 --> 00:00:08.260
We're actually going to do
two challenges for these, for

3
00:00:08.260 --> 00:00:10.160
the dictionary sort of things.

4
00:00:10.160 --> 00:00:13.860
So the first one, let me introduce,
I'm gonna copy this code because

5
00:00:13.860 --> 00:00:17.540
ultimately we're going to be using
that and I'm gonna create a new file.

6
00:00:17.540 --> 00:00:19.350
A new Python File.

7
00:00:19.350 --> 00:00:20.360
And we'll call this challenge.

8
00:00:22.750 --> 00:00:23.830
I'm just gonna paste it in there.

9
00:00:23.830 --> 00:00:27.960
That's the standard code that we
worked on in the previous video.

10
00:00:27.960 --> 00:00:30.320
But what we're going to do,
come up to the top here.

11
00:00:32.730 --> 00:00:36.540
We're gonna paste in First challenge,
bearing in mind there's a couple of

12
00:00:36.540 --> 00:00:38.670
challenges here, and
we saw a couple of sections.

13
00:00:38.670 --> 00:00:43.560
So the challenge at the moment is to
modify the program that you see below, so

14
00:00:43.560 --> 00:00:47.210
that the exits are a dictionary
rather than a list.

15
00:00:47.210 --> 00:00:50.180
And the keys being the numbers of
the locations and the values being

16
00:00:50.180 --> 00:00:53.680
dictionaries holding the exits, and
obviously they're doing that at present.

17
00:00:53.680 --> 00:00:57.080
So no change should be needed
to the actual code itself,

18
00:00:57.080 --> 00:01:00.810
it's just basically the dictionaries and
lists that you're changing.

19
00:01:00.810 --> 00:01:01.820
And once that's working,

20
00:01:01.820 --> 00:01:06.420
we're gonna create another dictionary
that contains words That players can use.

21
00:01:06.420 --> 00:01:08.030
Instructions, in other words.

22
00:01:08.030 --> 00:01:10.130
And these words will be the keys, and

23
00:01:10.130 --> 00:01:14.813
the valleys will be a single letter that
the can use to determine which way to go.

24
00:01:14.813 --> 00:01:16.600
So that's the challenge.

25
00:01:16.600 --> 00:01:17.760
Two components of a challenge.

26
00:01:17.760 --> 00:01:21.400
And bearing in mind it's also a secondary
challenge which you will be doing later.

27
00:01:21.400 --> 00:01:24.080
So go away and
see if you can complete both of those and

28
00:01:24.080 --> 00:01:28.740
once you're ready come back and we'll work
through both parts of this challenge.

29
00:01:28.740 --> 00:01:29.440
Pause the video now.

30
00:01:32.430 --> 00:01:33.370
Okay, so how did you get on?

31
00:01:33.370 --> 00:01:36.720
Hopefully you managed to resolve that and
you've got it working.

32
00:01:36.720 --> 00:01:40.180
So the first stage is actually quite easy
so what we really want to do here is just

33
00:01:40.180 --> 00:01:45.840
change exits From a dictionary or sorry
from a list I should say to a dictionary.

34
00:01:45.840 --> 00:01:47.200
So let's go ahead now and make the change.

35
00:01:47.200 --> 00:01:47.740
Want to go ahead and

36
00:01:47.740 --> 00:01:51.490
convert the existing list which
is on line 18 into a dictionary.

37
00:01:51.490 --> 00:01:55.200
So to do that we're going to start by
removing the square brackets which

38
00:01:55.200 --> 00:01:56.300
indicate that it's a list.

39
00:01:59.300 --> 00:02:01.390
Like so and I'll just put a bit of
space here so it's a bit clearer.

40
00:02:02.480 --> 00:02:06.696
That we also need to put our keys in for
each part so zero colon,

41
00:02:06.696 --> 00:02:10.849
one colon,

42
00:02:10.849 --> 00:02:15.055
two colon.

43
00:02:15.055 --> 00:02:21.745
Three column, four column,
and five column.

44
00:02:21.745 --> 00:02:24.295
So the keys are obviously the rooms.

45
00:02:24.295 --> 00:02:25.715
The locations as they are before.

46
00:02:25.715 --> 00:02:28.845
And I'll just clear that
up a little bit like so.

47
00:02:28.845 --> 00:02:30.625
And that should be all we need to do.

48
00:02:30.625 --> 00:02:33.205
We've converted it now from
a list to a dictionary.

49
00:02:33.205 --> 00:02:36.092
If a key being the location 0, 1, 2, 3, 4,

50
00:02:36.092 --> 00:02:40.600
5 Which matches our location dictionary
above, so if we run that, and

51
00:02:43.460 --> 00:02:47.200
we should still be able to go
say north you're in the forest,

52
00:02:47.200 --> 00:02:52.700
south you're standing at the end of
a road we can quit, he's sitting

53
00:02:52.700 --> 00:02:55.450
in front of a computer learning Python so
that's the first part of the challenge.

54
00:02:56.560 --> 00:02:58.150
Converting it to a dictionary and

55
00:02:58.150 --> 00:03:01.520
note how we didn't have to change
any of the code that's the beauty

56
00:03:01.520 --> 00:03:05.980
that if we're using a numerical key for
a dictionary, the syntax for retrieving

57
00:03:05.980 --> 00:03:10.400
the dictionary value by key is the same
as retrieving a list item by index.

58
00:03:10.400 --> 00:03:13.280
That's one of the great things that
happened here, the code doesn't have to

59
00:03:13.280 --> 00:03:17.870
change to accommodate The change in the
data structure from list to dictionary.

60
00:03:17.870 --> 00:03:19.430
Okay so for the second part so

61
00:03:19.430 --> 00:03:23.530
we need to create a dictionary whose
keys are the words we're interested and

62
00:03:23.530 --> 00:03:26.680
the values of the single letter
that the program expects.

63
00:03:26.680 --> 00:03:30.410
So if the pro players talks
more than a single letter.

64
00:03:30.410 --> 00:03:32.630
Then we use the vocabulary dictionary.

65
00:03:32.630 --> 00:03:35.420
Because they could type
something like run less quickly,

66
00:03:35.420 --> 00:03:38.430
we don't use the text as the value to
look up, but we do it the other way.

67
00:03:38.430 --> 00:03:40.870
We iterate through the keys
to see if their text

68
00:03:40.870 --> 00:03:43.360
contains one of the words
that we recognize.

69
00:03:43.360 --> 00:03:47.540
So, what we need to do first is create our
vocabulary, we're going to put it down

70
00:03:47.540 --> 00:03:50.130
here and that's going to be a dictionary
with the relevant commands.

71
00:03:51.320 --> 00:03:58.120
So, we're going to start by
typing vocabulary equals and

72
00:03:58.120 --> 00:04:02.673
the first one will be quit and
the key, the value will be two.

73
00:04:02.673 --> 00:04:11.816
North, north, south,

74
00:04:16.537 --> 00:04:19.815
east, and west.

75
00:04:19.815 --> 00:04:24.720
[SOUND] And
we can just tidy it up a little bit so

76
00:04:24.720 --> 00:04:26.720
it sits there nicely, but that's optional.

77
00:04:26.720 --> 00:04:29.120
So we've now assigned the vocabulary.

78
00:04:29.120 --> 00:04:29.900
The dictionary.

79
00:04:29.900 --> 00:04:32.660
We've assigned and created a dictionary
and assigned it to vocabulary.

80
00:04:32.660 --> 00:04:33.650
The variable.

81
00:04:33.650 --> 00:04:35.780
So what we want to do
now is add some codes.

82
00:04:35.780 --> 00:04:38.750
So once we've actually got a command
that's been given to us and

83
00:04:38.750 --> 00:04:40.210
the users selected that and typed it in.

84
00:04:40.210 --> 00:04:42.530
Down here we want to
start adding some code.

85
00:04:42.530 --> 00:04:47.559
So we want to parse the input so
we're gonna parse user

86
00:04:47.559 --> 00:04:55.980
report using our vocabulary
dictionary if necessary.

87
00:04:57.620 --> 00:05:00.260
And we're only going to do that remember
if the length is greater than one.

88
00:05:00.260 --> 00:05:07.240
So I'm going to put if, len, direction,
direction, greater than one.

89
00:05:09.300 --> 00:05:14.370
In other words, more than one letter.

90
00:05:14.370 --> 00:05:16.430
Check out vocab.

91
00:05:16.430 --> 00:05:19.940
Then we put four word in vocabulary.

92
00:05:21.770 --> 00:05:26.790
So what effectively we're doing now
is does it contain a word we know?

93
00:05:29.420 --> 00:05:35.580
If word in direction,
if it does then direction,

94
00:05:35.580 --> 00:05:40.464
direction becomes equal
to vocabulary(word) and

95
00:05:40.464 --> 00:05:42.620
we'll just clean it up a little bit.

96
00:05:42.620 --> 00:05:45.280
And that's actually it
as you can see then.

97
00:05:45.280 --> 00:05:47.660
Remember, we're also converting
it to upper case as well.

98
00:05:47.660 --> 00:05:50.100
So we're really only testing
to see whatever they have

99
00:05:50.100 --> 00:05:52.910
typed is greater than 1, so
more than one character.

100
00:05:52.910 --> 00:05:57.160
If it is, we're gonna go through our
dictionary and try to find a match for

101
00:05:57.160 --> 00:05:57.980
whatever they have typed.

102
00:05:57.980 --> 00:06:00.080
And if they have typed
something like north,

103
00:06:00.080 --> 00:06:03.030
we're gonna match it back to
the value N as you can see there.

104
00:06:03.030 --> 00:06:04.750
Let's actually run this and
see if it works.

105
00:06:04.750 --> 00:06:06.970
So, first thing, you should just check.

106
00:06:06.970 --> 00:06:09.160
If you go north, you're in a forest.

107
00:06:09.160 --> 00:06:11.080
South, you're standing in the road.

108
00:06:11.080 --> 00:06:15.120
And if you type north, you're in a forest.

109
00:06:16.980 --> 00:06:19.340
But also you should be able to type,
go north.

110
00:06:20.990 --> 00:06:25.540
Your gonna first go south,
and the reason is

111
00:06:25.540 --> 00:06:29.520
we're actually done looking at our and
we're going through our dictionary and

112
00:06:29.520 --> 00:06:32.510
we're comparing each word of
the dictionary to see whether it's fine or

113
00:06:32.510 --> 00:06:37.500
whatevers being So, the entire string is
going south We are checking to see if

114
00:06:37.500 --> 00:06:40.420
the word South is actually in that string
and that's why it's working that way

115
00:06:40.420 --> 00:06:45.210
even though we've typed extra letters that
are not in it, exact match so to speak.

116
00:06:45.210 --> 00:06:47.380
So what we now got is
a fairly flexible way for

117
00:06:47.380 --> 00:06:50.840
players to specify which
direction they'd like to go in.

118
00:06:50.840 --> 00:06:53.930
And for that reason alone hopefully
that's demonstrated the power of using

119
00:06:53.930 --> 00:06:54.640
dictionaries.

120
00:06:54.640 --> 00:06:58.860
Once you are actually used to using
dictionaries Even our exits one.

121
00:06:58.860 --> 00:07:02.940
The exits diction where you will be
converted makes a lot more sense, but

122
00:07:02.940 --> 00:07:06.130
you can probably see why we chose
to use a list initially and

123
00:07:06.130 --> 00:07:08.640
that's because a dictionary
of dictionaries

124
00:07:08.640 --> 00:07:10.845
can look confusing at first until
you sort of understand the.

125
00:07:10.845 --> 00:07:11.475
Concepts.

126
00:07:11.475 --> 00:07:14.305
Now with that said, we can make
the program a bit more efficient though.

127
00:07:14.305 --> 00:07:17.925
So it's quite likely that our
vocabulary will grow quite large,

128
00:07:17.925 --> 00:07:21.015
whereas the text the players type
in will only be a few words.

129
00:07:21.015 --> 00:07:21.675
So as a result,

130
00:07:21.675 --> 00:07:25.310
it's really not efficient to perform
the word lookup the way we have.

131
00:07:25.310 --> 00:07:29.720
As we could literally end up iterating
through a large collection of keys before

132
00:07:29.720 --> 00:07:32.550
we find the one that's
in the player's input,

133
00:07:32.550 --> 00:07:34.140
that's contained in the player's input.

134
00:07:34.140 --> 00:07:38.060
A better way would be to check each
word that the player has typed to

135
00:07:38.060 --> 00:07:39.900
see if it's in the vocabulary.

136
00:07:39.900 --> 00:07:43.540
Cuz obviously, starting from that way,
rather than coming from the.

137
00:07:43.540 --> 00:07:45.770
Starting at the vocabulary and
going through that.

138
00:07:45.770 --> 00:07:46.600
Better to go the other way.

139
00:07:46.600 --> 00:07:49.150
And Python provides a way to do just that.

140
00:07:49.150 --> 00:07:52.010
So what we need to do is break up
the input that the [INAUDIBLE].

141
00:07:52.010 --> 00:07:56.260
Applies topped into individual words
in other words individual sequences of

142
00:07:56.260 --> 00:08:00.640
characters separated by spaces so really
what we want to do there is we want to do

143
00:08:00.640 --> 00:08:04.850
the opposite of join and in fact there is
a method to do that and its called split.

144
00:08:04.850 --> 00:08:06.550
And it does exactly what we want.

145
00:08:06.550 --> 00:08:11.290
So given a string,
the split command or the split

146
00:08:11.290 --> 00:08:15.880
method will split a string into a list
containing all the parts of the string

147
00:08:15.880 --> 00:08:20.320
that are separated by the delimiter of our
choice, which is gonna be a space here.

148
00:08:20.320 --> 00:08:24.010
And if we don't specify a delimiter,
it defaults to a space.

149
00:08:24.010 --> 00:08:24.920
But we could use commas,

150
00:08:24.920 --> 00:08:28.540
colons or any other type of text
that we want as a delimiter.

151
00:08:28.540 --> 00:08:30.560
So let's have a look at,
see that in action.

152
00:08:30.560 --> 00:08:33.860
What we want to do before we start,
we want to comment

153
00:08:33.860 --> 00:08:36.360
out the call of the [INAUDIBLE] So
I'm going to close this down.

154
00:08:37.500 --> 00:08:38.820
Disconnect.

155
00:08:38.820 --> 00:08:42.090
Let's go ahead and comment all that
code out for now, cuz we don't need it.

156
00:08:42.090 --> 00:08:43.560
Come back to that later.

157
00:08:43.560 --> 00:08:47.350
Comment all that out again with command
slash, which is control slash for

158
00:08:47.350 --> 00:08:53.070
Windows and Linux after selecting it, and
we'll put our code up here We're probably

159
00:08:53.070 --> 00:08:56.676
coming to that area as well, the lock = 1
because that's all part and parcel of it.

160
00:08:56.676 --> 00:08:59.570
So let's actually try the split function,
let's do a couple of examples.

161
00:08:59.570 --> 00:09:03.920
We can do a print locations 0.

162
00:09:03.920 --> 00:09:12.540
split, and also try print locations 3.

163
00:09:12.540 --> 00:09:13.360
split.

164
00:09:15.100 --> 00:09:16.380
Passing a parameter this time.

165
00:09:16.380 --> 00:09:17.590
I was, or, comma.

166
00:09:19.490 --> 00:09:20.740
And let's also try this one.

167
00:09:20.740 --> 00:09:22.031
Print.
Space.

168
00:09:22.031 --> 00:09:22.559
Dot.

169
00:09:22.559 --> 00:09:24.842
Join locations.

170
00:09:24.842 --> 00:09:25.545
Zero.

171
00:09:25.545 --> 00:09:26.073
Dot.

172
00:09:26.073 --> 00:09:27.127
Spirit.

173
00:09:27.127 --> 00:09:33.220
[SOUND] So, let's run this.

174
00:09:33.220 --> 00:09:35.970
So you can see what happened
with the first one.

175
00:09:35.970 --> 00:09:39.750
It splits, you are sitting in front of
a computer learning Python, into a list

176
00:09:39.750 --> 00:09:43.350
containing the 10 words, which is pretty
cool that it's done that automatically.

177
00:09:43.350 --> 00:09:47.940
The 2nd example gave a list, gives a list
containing 2 items, as you can see,

178
00:09:47.940 --> 00:09:52.650
because it's split based on the fact that
we passed the parameter of a comma, so

179
00:09:52.650 --> 00:09:56.860
it's using that a as a delimiter
instead of the default being a space.

180
00:09:56.860 --> 00:09:59.810
Which the split method will use
unless you give it a parameter.

181
00:09:59.810 --> 00:10:02.800
And incidentally if you didn't want
a leading space in the second list item,

182
00:10:02.800 --> 00:10:06.840
you could specify comma as a string to
split on if you wanted to do it that way.

183
00:10:06.840 --> 00:10:08.710
So split's the opposite of join so

184
00:10:08.710 --> 00:10:12.910
the final print is interesting if
as it turns out a little futile.

185
00:10:12.910 --> 00:10:18.260
So it uses split to split the text that
spaces, but then it also calls join

186
00:10:18.260 --> 00:10:21.190
on a string containing a single
space to join them back up again.

187
00:10:21.190 --> 00:10:24.170
So really the end result is the orignal
string that you worked with.

188
00:10:24.170 --> 00:10:26.240
Ok, so armed with this split method,

189
00:10:26.240 --> 00:10:29.640
we can rewrite the program to
work the correct way around.

190
00:10:29.640 --> 00:10:32.660
So I can check the players
input against the vocabulary,

191
00:10:32.660 --> 00:10:33.970
instead of the other way around.

192
00:10:33.970 --> 00:10:35.360
So let's go back and do that.

193
00:10:35.360 --> 00:10:40.690
And I'm going to comment these [INAUDIBLE]
out, like so, and I'm going to select

194
00:10:40.690 --> 00:10:44.975
the [INAUDIBLE] code that we Comment
it out, and do a command slash again.

195
00:10:44.975 --> 00:10:47.877
Just control slash on Windows and
Linux, and that makes it,

196
00:10:47.877 --> 00:10:51.335
more [INAUDIBLE] gets rid of the comments,
so that we can work on it again.

197
00:10:51.335 --> 00:10:53.205
So what we want to do here is see,

198
00:10:53.205 --> 00:10:56.765
in this method is this part here
after the [INAUDIBLE] direction.

199
00:10:56.765 --> 00:10:58.898
You really just want to
comment that out for now.

200
00:10:58.898 --> 00:11:00.800
[INAUDIBLE] I'll do is I'll delete that.

201
00:11:00.800 --> 00:11:04.300
So after the test to make sure that what's
been taught has more than one characters

202
00:11:04.300 --> 00:11:09.760
in it,
we do words equals direction of split.

203
00:11:09.760 --> 00:11:14.260
So we're splitting up the input using
the default delimiter of a space.

204
00:11:14.260 --> 00:11:17.300
Cuz we're gonna go through those words,
so for word in words.

205
00:11:18.400 --> 00:11:22.600
And we're going a test the other way
this time and we're putting if word In

206
00:11:23.960 --> 00:11:29.550
vocabulary direction
equals vocabulary word.

207
00:11:29.550 --> 00:11:32.080
And we can also break at that point.

208
00:11:33.380 --> 00:11:36.350
So you can see how we've
done it the other way now.

209
00:11:36.350 --> 00:11:40.660
So what we've done is we've taken doing
our searching based on what the users

210
00:11:40.660 --> 00:11:45.280
typed instead of going through the whole
dictionary, which Isn't a problem now, but

211
00:11:45.280 --> 00:11:48.380
if we started having hundreds of entries,
it could start slowing it down.

212
00:11:48.380 --> 00:11:52.430
So it's always something that you should
be looking at when you're developing code,

213
00:11:52.430 --> 00:11:54.960
to decide which angle should I start from.

214
00:11:54.960 --> 00:11:57.670
Is it best to start, in this case,
from the user's input,

215
00:11:57.670 --> 00:12:00.120
because chances are there's only
gonna be a few words there,

216
00:12:00.120 --> 00:12:03.880
instead of automatically processing
the entire dictionary each time,

217
00:12:03.880 --> 00:12:05.950
which we did in sort of
the first version of this code.

218
00:12:05.950 --> 00:12:07.489
Let's run this and make sure it works.

219
00:12:08.900 --> 00:12:12.110
So if we type east, okay, and

220
00:12:12.110 --> 00:12:16.620
now back to west again, and
if we type E, go back to west again.

221
00:12:18.800 --> 00:12:20.000
Please sir, can I go east.

222
00:12:22.114 --> 00:12:25.820
And it's gonna say it's found east,
so it's gonna [INAUDIBLE]

223
00:12:25.820 --> 00:12:29.580
each one of those words and found east
as the last word, And that works.

224
00:12:29.580 --> 00:12:30.490
So we go back west again.

225
00:12:30.490 --> 00:12:33.590
And just to make sure,

226
00:12:33.590 --> 00:12:39.020
how bout going east now again.

227
00:12:39.020 --> 00:12:39.990
And still found that as well.

228
00:12:41.000 --> 00:12:41.820
So that's it.
I hope

229
00:12:41.820 --> 00:12:43.110
you got a lot out of that challenge.

230
00:12:43.110 --> 00:12:45.170
So we're not done yet with dictionaries.

231
00:12:45.170 --> 00:12:48.530
In the next video, we're gonna go ahead
and continue our work on dictionaries.

232
00:12:48.530 --> 00:12:51.120
And specifically we're going to
be looking at the update method

233
00:12:51.120 --> 00:12:53.380
which allows you to
combine two dictionaries.

234
00:12:53.380 --> 00:12:57.230
And also a copy method that's used
to create a copy of a dictionary and

235
00:12:57.230 --> 00:12:59.930
then we'll go into another challenge for
that as well.

236
00:12:59.930 --> 00:13:01.080
So see you in the next video.