Repository navigation
Expand file tree
/
Copy patherrors_and_exceptions.html
More file actions
234 lines (193 loc) · 16.2 KB
/
Copy patherrors_and_exceptions.html
File metadata and controls
234 lines (193 loc) · 16.2 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta http-equiv="last-modified" content="2020-11-30 19:49:51 +0000">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- meta "search-domain" used for google site search function google_search() -->
<meta name="search-domain" value="https://swcarpentry.github.io/python-novice-inflammation">
<link rel="stylesheet" type="text/css" href="https://swcarpentry.github.io/python-novice-inflammation/assets/css/bootstrap.css" />
<link rel="stylesheet" type="text/css" href="https://swcarpentry.github.io/python-novice-inflammation/assets/css/bootstrap-theme.css" />
<link rel="stylesheet" type="text/css" href="https://swcarpentry.github.io/python-novice-inflammation/assets/css/lesson.css" />
<link rel="stylesheet" type="text/css" href="https://swcarpentry.github.io/python-novice-inflammation/assets/css/syntax.css" />
<link rel="license" href="#license-info" />
<!-- Favicons for everyone -->
<link rel="apple-touch-icon-precomposed" sizes="57x57" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-57x57.png" />
<link rel="apple-touch-icon-precomposed" sizes="114x114" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-114x114.png" />
<link rel="apple-touch-icon-precomposed" sizes="72x72" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-72x72.png" />
<link rel="apple-touch-icon-precomposed" sizes="144x144" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-144x144.png" />
<link rel="apple-touch-icon-precomposed" sizes="60x60" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-60x60.png" />
<link rel="apple-touch-icon-precomposed" sizes="120x120" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-120x120.png" />
<link rel="apple-touch-icon-precomposed" sizes="76x76" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-76x76.png" />
<link rel="apple-touch-icon-precomposed" sizes="152x152" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/apple-touch-icon-152x152.png" />
<link rel="icon" type="image/png" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/favicon-196x196.png" sizes="196x196" />
<link rel="icon" type="image/png" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/favicon-96x96.png" sizes="96x96" />
<link rel="icon" type="image/png" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/favicon-32x32.png" sizes="32x32" />
<link rel="icon" type="image/png" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/favicon-16x16.png" sizes="16x16" />
<link rel="icon" type="image/png" href="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/favicon-128.png" sizes="128x128" />
<meta name="application-name" content="Software Carpentry - Programming with Python"/>
<meta name="msapplication-TileColor" content="#FFFFFF" />
<meta name="msapplication-TileImage" content="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/mstile-144x144.png" />
<meta name="msapplication-square70x70logo" content="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/mstile-70x70.png" />
<meta name="msapplication-square150x150logo" content="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/mstile-150x150.png" />
<meta name="msapplication-wide310x150logo" content="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/mstile-310x150.png" />
<meta name="msapplication-square310x310logo" content="https://swcarpentry.github.io/python-novice-inflammation/assets/favicons/swc/mstile-310x310.png" />
<!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
<!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
<script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->
<title>
Additional Exercises – Programming with Python
</title>
</head>
<body>
<div class="container">
<h1 class="maintitle">Errors and Exceptions - Exercises</h1>
<blockquote class="challenge">
<blockquote class="challenge">
<h2 id="reading-error-messages">Reading Error Messages</h2>
<p>Read the Python code and the resulting traceback below, and answer the following questions:</p>
<ol>
<li>How many levels does the traceback have?</li>
<li>What is the function name where the error occurred?</li>
<li>On which line number in this function did the error occur?</li>
<li>What is the type of error?</li>
<li>What is the error message?</li>
</ol>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># This code has an intentional error. Do not type it directly;
# use it for reference to understand the error message below.
</span><span class="k">def</span> <span class="nf">print_message</span><span class="p">(</span><span class="n">day</span><span class="p">):</span>
<span class="n">messages</span> <span class="o">=</span> <span class="p">{</span>
<span class="s">'monday'</span><span class="p">:</span> <span class="s">'Hello, world!'</span><span class="p">,</span>
<span class="s">'tuesday'</span><span class="p">:</span> <span class="s">'Today is Tuesday!'</span><span class="p">,</span>
<span class="s">'wednesday'</span><span class="p">:</span> <span class="s">'It is the middle of the week.'</span><span class="p">,</span>
<span class="s">'thursday'</span><span class="p">:</span> <span class="s">'Today is Donnerstag in German!'</span><span class="p">,</span>
<span class="s">'friday'</span><span class="p">:</span> <span class="s">'Last day of the week!'</span><span class="p">,</span>
<span class="s">'saturday'</span><span class="p">:</span> <span class="s">'Hooray for the weekend!'</span><span class="p">,</span>
<span class="s">'sunday'</span><span class="p">:</span> <span class="s">'Aw, the weekend is almost over.'</span>
<span class="p">}</span>
<span class="k">print</span><span class="p">(</span><span class="n">messages</span><span class="p">[</span><span class="n">day</span><span class="p">])</span>
<span class="k">def</span> <span class="nf">print_friday_message</span><span class="p">():</span>
<span class="n">print_message</span><span class="p">(</span><span class="s">'Friday'</span><span class="p">)</span>
<span class="n">print_friday_message</span><span class="p">()</span>
</code></pre></div> </div>
<div class="language-plaintext error highlighter-rouge"><div class="highlight"><pre class="highlight"><code>---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-1-4be1945adbe2> in <module>()
14 print_message('Friday')
15
---> 16 print_friday_message()
<ipython-input-1-4be1945adbe2> in print_friday_message()
12
13 def print_friday_message():
---> 14 print_message('Friday')
15
16 print_friday_message()
<ipython-input-1-4be1945adbe2> in print_message(day)
9 'sunday': 'Aw, the weekend is almost over.'
10 }
---> 11 print(messages[day])
12
13 def print_friday_message():
KeyError: 'Friday'
</code></pre></div> </div>
<blockquote class="solution">
<h2 id="solution">Solution</h2>
<ol>
<li>3 levels</li>
<li><code class="language-plaintext highlighter-rouge">print_message</code></li>
<li>11</li>
<li><code class="language-plaintext highlighter-rouge">KeyError</code></li>
<li>There isn’t really a message; you’re supposed to infer that <code class="language-plaintext highlighter-rouge">Friday</code> is not a key in <code class="language-plaintext highlighter-rouge">messages</code>.</li>
</ol>
</blockquote>
</blockquote>
<blockquote class="challenge">
<h2 id="identifying-syntax-errors">Identifying Syntax Errors</h2>
<ol>
<li>Read the code below, and (without running it) try to identify what the errors are.</li>
<li>Run the code, and read the error message. Is it a <code class="language-plaintext highlighter-rouge">SyntaxError</code> or an <code class="language-plaintext highlighter-rouge">IndentationError</code>?</li>
<li>Fix the error.</li>
<li>Repeat steps 2 and 3, until you have fixed all the errors.</li>
</ol>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">def</span> <span class="nf">another_function</span>
<span class="k">print</span><span class="p">(</span><span class="s">'Syntax errors are annoying.'</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">'But at least Python tells us about them!'</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">'So they are usually not too hard to fix.'</span><span class="p">)</span>
</code></pre></div> </div>
<blockquote class="solution">
<h2 id="solution-1">Solution</h2>
<p><code class="language-plaintext highlighter-rouge">SyntaxError</code> for missing <code class="language-plaintext highlighter-rouge">():</code> at end of first line,
<code class="language-plaintext highlighter-rouge">IndentationError</code> for mismatch between second and third lines.
A fixed version is:</p>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">def</span> <span class="nf">another_function</span><span class="p">():</span>
<span class="k">print</span><span class="p">(</span><span class="s">'Syntax errors are annoying.'</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">'But at least Python tells us about them!'</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="s">'So they are usually not too hard to fix.'</span><span class="p">)</span>
</code></pre></div> </div>
</blockquote>
</blockquote>
<blockquote class="challenge">
<h2 id="identifying-variable-name-errors">Identifying Variable Name Errors</h2>
<ol>
<li>Read the code below, and (without running it) try to identify what the errors are.</li>
<li>Run the code, and read the error message.
What type of <code class="language-plaintext highlighter-rouge">NameError</code> do you think this is?
In other words, is it a string with no quotes,
a misspelled variable,
or a variable that should have been defined but was not?</li>
<li>Fix the error.</li>
<li>Repeat steps 2 and 3, until you have fixed all the errors.</li>
</ol>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">for</span> <span class="n">number</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">):</span>
<span class="c1"># use a if the number is a multiple of 3, otherwise use b
</span> <span class="k">if</span> <span class="p">(</span><span class="n">Number</span> <span class="o">%</span> <span class="mi">3</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="n">message</span> <span class="o">+</span> <span class="n">a</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="n">message</span> <span class="o">+</span> <span class="s">'b'</span>
<span class="k">print</span><span class="p">(</span><span class="n">message</span><span class="p">)</span>
</code></pre></div> </div>
<blockquote class="solution">
<h2 id="solution-2">Solution</h2>
<p>3 <code class="language-plaintext highlighter-rouge">NameError</code>s for <code class="language-plaintext highlighter-rouge">number</code> being misspelled, for <code class="language-plaintext highlighter-rouge">message</code> not defined,
and for <code class="language-plaintext highlighter-rouge">a</code> not being in quotes.</p>
<p>Fixed version:</p>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">message</span> <span class="o">=</span> <span class="s">''</span>
<span class="k">for</span> <span class="n">number</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">):</span>
<span class="c1"># use a if the number is a multiple of 3, otherwise use b
</span> <span class="k">if</span> <span class="p">(</span><span class="n">number</span> <span class="o">%</span> <span class="mi">3</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="n">message</span> <span class="o">+</span> <span class="s">'a'</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">message</span> <span class="o">=</span> <span class="n">message</span> <span class="o">+</span> <span class="s">'b'</span>
<span class="k">print</span><span class="p">(</span><span class="n">message</span><span class="p">)</span>
</code></pre></div> </div>
</blockquote>
</blockquote>
<blockquote class="challenge">
<h2 id="identifying-index-errors">Identifying Index Errors</h2>
<ol>
<li>Read the code below, and (without running it) try to identify what the errors are.</li>
<li>Run the code, and read the error message. What type of error is it?</li>
<li>Fix the error.</li>
</ol>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">seasons</span> <span class="o">=</span> <span class="p">[</span><span class="s">'Spring'</span><span class="p">,</span> <span class="s">'Summer'</span><span class="p">,</span> <span class="s">'Fall'</span><span class="p">,</span> <span class="s">'Winter'</span><span class="p">]</span>
<span class="k">print</span><span class="p">(</span><span class="s">'My favorite season is '</span><span class="p">,</span> <span class="n">seasons</span><span class="p">[</span><span class="mi">4</span><span class="p">])</span>
</code></pre></div> </div>
<blockquote class="solution">
<h2 id="solution-3">Solution</h2>
<p><code class="language-plaintext highlighter-rouge">IndexError</code>; the last entry is <code class="language-plaintext highlighter-rouge">seasons[3]</code>, so <code class="language-plaintext highlighter-rouge">seasons[4]</code> doesn’t make sense.
A fixed version is:</p>
<div class="language-python highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">seasons</span> <span class="o">=</span> <span class="p">[</span><span class="s">'Spring'</span><span class="p">,</span> <span class="s">'Summer'</span><span class="p">,</span> <span class="s">'Fall'</span><span class="p">,</span> <span class="s">'Winter'</span><span class="p">]</span>
<span class="k">print</span><span class="p">(</span><span class="s">'My favorite season is '</span><span class="p">,</span> <span class="n">seasons</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
</code></pre></div> </div>
</blockquote>
</blockquote>
</article>
</div>
<script src="https://swcarpentry.github.io/python-novice-inflammation/assets/js/jquery.min.js"></script>
<script src="https://swcarpentry.github.io/python-novice-inflammation/assets/js/bootstrap.min.js"></script>
<script src="https://swcarpentry.github.io/python-novice-inflammation/assets/js/lesson.js"></script>
</body>
</html>