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SENG265 ASSIGNMENT 4

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SENG265
ASSIGNMENT 4

1 Assignment Overview
The HTML language, which is used to describe the layout and content of web pages,
has a famously verbose syntax: relatively simple formatting and layout instructions
can often require several layers of bulky HTML tags. Modern HTML is very flexible
for specifying visual aspects of the displayed content. However, extracting information from the HTML representation can be difficult. The goal of this assignment is
to write a Python 3 table_to_csv.py program which converts HTML tables to a
CSV representation.
Section 2 describes HTML Tables, Section 3 contains the Specification for the
program you are expected to write as well as an example input HTML and expected
CSV representation. Section 4 provides some Implementation advice. Finally, Section 6 describes the Testing component and the testing files you are provided with,
What you should Submit is outlined in Section 7 and the Evaluation scheme is
given in Section 8. Your code is expected to run without warnings in the course
lab (ECS 342) using Python 3.4.3.
2 HTML Tables
Tables in HTML are specified with the <table> tag. A brief tutorial on the <table>
tag, along with interactive examples, can be found at
http://www.w3schools.com/html/html tables.asp. Note that whitespace in HTML
is generally ignored: spaces, newlines and tabs are collapsed into a single space
when the page is rendered. Line breaks are specified by the <br /> tag. Consider
the HTML table below (which appears as the first example in the tutorial linked
above).
<table style=”width:100%”>
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
</tr>
<tr>
<td>Jill</td>
<td>Smith</td>
<td>50</td>
</tr>
<tr>
<td>Eve</td>
<td>Jackson</td>
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<td>94</td>
</tr>
</table>
The table described by the HTML code above would be rendered by a web browser
in a similar format to the table below.
Firstname Lastname Age
Jill Smith 50
Eve Jackson 94
The <tr> and </tr> tags enclose the data for each row of the table, and the <td>
and </td> tags enclose the contents of each cell. The <th> and </th> tags enclose
the contents of header cells, but their use is optional (some authors use regular
<td> tags for header cells). Cells of a table may contain HTML code, including
other HTML tables.
Tag names are not case sensitive, so ‘<tD>’ and ‘<TD>’ are both valid forms of the
‘<td>’ tag. Any HTML tag may contain attributes that change its appearance.
The most common attribute in modern HTML is ‘style’. For example, make the
contents of a particular cell boldfaced, the attribute style=”font-weight: bold;”
can be added to the <td> tag:
<td style=”font-weight: bold;”>Jill</td>
Additionally, any HTML tag may contain whitespace after the tag name, between
attributes or before the closing ‘>’ character. Whitespace is not permitted between
the opening ‘<’ character and the tag name. For example, ‘<td >’ and ‘</td >’
are valid tags, but ‘< /td>’ and ‘< td >’ are not.
Since whitespace in HTML is generally ignored, there is no requirement that the
table be laid out in a readable way in the HTML code. The table in the example
above could also be represented by the code below.
<table style=”width:100%”> <tr > <th >Firstname</th ><th>
Lastname</th><th>Age</th></tr ><tr><td>Jill</td>
<td>Smith</td><td >50</td>
</tr><tr><td>Eve</td><td>Jackson</td> <td>94</td></tr></table>
This assignment assumes the following extra constraints to any basic HTML table
specification used as test input file.
• To be considered valid, a test input must be valid HTML. For example, tags
like <td> can only occur inside of a <tr> tag, which in turn must be inside
a <table> tag. All opening tags must have a matching closing tag (note that
some HTML tags, like <br />, are singular and do not need a closing tag),
and vice versa.
• Between the opening angle bracket (<) and closing angle bracket (>) of a tag,
no other instances of closing angle brackets are permitted (including inside of
attributes).
• Commas may not appear inside the data for a cell. However, other aspects of
the HTML which are not cell content (such as the style attributes of <td>
tags) may contain commas.
• Cells may contain any data, including other HTML tags, but may not contain
nested <table> tags. The prohibition on comma use applies to all contents of
each cell, including HTML tags. In other words, if the comma character
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appears between the opening <td> tag and its matching </td> tag,
the input will be considered invalid.
• There is no requirement that each row of the table contain the same number
of columns.
• Every HTML table must have at least one row.
• Every row of an HTML table must contain at least one cell.
• The rowspan and colspan, which are used to make cells span multiple rows
or columns, are not permitted.
3 HTML-to-CSV Converter
Your task is to write a Python 3 program called table_to_csv.py which reads
HTML from standard input and outputs a CSV representation of each table in
the input, including any header cells specified with <th> (if present).
The resulting CSV data will be printed to standard output in the following format:
TABLE 1:
<CSV data for first table in the input>
TABLE 2:
<CSV data for the second table in the input>
TABLE 3:
<CSV data for the third table in the input>

Your implementation may assume that the input table complies with the constraints
given in the previous section, and must also meet the following requirements.
• All runs of one or more spaces, newlines, tabs, or other whitespace should be
collapsed into a single space.
• Within a table cell, all HTML tags are to be left intact.
• The contents of each table cell should be stripped of all leading and trailing
whitespace before being output. For example, the cell ‘<td> Lemon Meringue </td>’
should be output as ‘Lemon Meringue’ (note that the multiple spaces between
the two words are also collapsed into one space).
• Every row of the output CSV spreadsheet must contain the same number of
columns (recall that the number of columns in a row of a CSV spreadsheet
is the number of commas in the row minus one). If the rows of the HTML
table contain a differing number of columns, then the number of columns in
the output spreadsheet should be equal to the number of columns in the row
of the input table with the largest number of columns. Other rows should be
padded with blank cells to meet the column requirement.
As an example, consider the following input HTML table below:
<table><tr>
<th>Student Number</th><th>Student Name</th><th>Major</th>
<th>A1 mark</th><th>A2 mark</th></tr >
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<tr><td>V00000001</td><td></td><td></td><td>10</td>
<td>11</td>
</tr>
<tr><td>V00123456</td><td>Alastair Avocado</td>
<td>Psychology</td><td>12</td><td></td></tr>
<tr >
<td>V00123457</td >
<td>Rebecca Raspberry
</td><td>Computer Science</td><td>17</td><td>14</td></tr>
<tr><td>V00314159</td><td>Fiona Framboise</td>
<td style=”font-family: monospace; font-size: 20pt; font-weight: bold;”>
Computer Science
</td>
<td> </td><td>17</td></tr>
<tr><td>V00654321</td><td>Meredith Malina</td>
<td style=”color: red;”>Software Engineering</td><td>18</td><td>12</td></tr>
<tr><td>V00654322</td><td>Hannah Hindbaer</td><td>Physics</td><td>15</td><td>18</td></tr>
<tr><td>V00951413</td><td>Neal Naranja</td><td>Anthropology</td><td>15</td><td>15</td></tr>
</table>
When provided as input to a correct HTML-to-CSV implementation, the HTML
table above would be converted to the following CSV representation.
TABLE 1:
Student Number,Student Name,Major,A1 mark,A2 mark
V00000001,,,10,11
V00123456,Alastair Avocado,Psychology,12,
V00123457,Rebecca Raspberry,Computer Science,17,14
V00314159,Fiona Framboise,Computer Science,,17
V00654321,Meredith Malina,Software Engineering,18,12
V00654322,Hannah Hindbaer,Physics,15,18
V00951413,Neal Naranja,Anthropology,15,15
4 Implementation Advice
Since HTML allows such a wide variation in the structure and formatting of tags,
the use of regular expressions to match each tag pair is encouraged. However, you
are not required to use regular expressions (or any other particular implementation
technique, as long as your code is valid Python 3). If you use regular expressions,
be aware of the following points.
• By default, the ‘.’ specifier does not match the newline character (‘\n’), so
if you are searching for something which crosses a line boundary, it will not
match. For example, the pattern ‘A.*B’ would match ‘Axy z B’ but not
‘Axy\n z B’ by default. Since whitespace in HTML can be collapsed to a
single space, you can remedy this problem by replacing all newlines characters with spaces. You can also use the ‘re.DOTALL’ flag when performing
regular expression matching, which will cause newlines to be matched by the
‘.’ specifier. Consider the interactive Python 3 session below, which contains
examples of both methods.
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>>> s1 = ’Axy z B’
>>> s2 = ’Axy\n z B’
>>> re.match(’A.*B’,s1)
<_sre.SRE_Match object; span=(0, 8), match=’Axy z B’>
>>> re.match(’A.*B’,s2)
>>> re.findall(’A.*B’,s1)
[’Axy z B’]
>>> re.findall(’A(.*)B’,s1)
[’xy z ’]
>>> re.findall(’A(.*)B’,s2)
[]
>>> re.findall(’A(.*)B’,s2, re.DOTALL)
[’xy\n z ’]
>>> s3 = s2.replace(’\n’,’ ’)
>>> s3
’Axy z B’
>>> re.findall(’A(.*)B’,s3)
[’xy z ’]
• Since HTML tag names are not case sensitive, you may want to use the
‘re.IGNORECASE’ flag to enable case-insensitive matching. Consider the interactive session below.
>>> x = ’abc’
>>> y = ’Abc’
>>> z = ’A——C’
>>> re.findall(’a.*c’,x)
[’abc’]
>>> re.findall(’a.*c’,y)
[]
>>> re.findall(’a.*c’,z)
[]
>>> re.findall(’a.*c’,y,re.IGNORECASE)
[’Abc’]
>>> re.findall(’a.*c’,z,re.IGNORECASE)
[’A——C’]
Note that if you want to use multiple flags (such as both ‘re.DOTALL’ and
‘re.IGNORECASE’), you can combine them with the bitwise-OR operator (for
example,
‘re.findall(’a.*c’,z, re.IGNORECASE|re.DOTALL)’).
5 Constraints
You may only use use python3 modules that are installed on ECS 342 or linux.csc.uvic.ca.
If an python3 module is not installed, you may not use that module in your code.
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6 Test Inputs
You should ensure that your programs handle error cases (such as files which do
not exist) appropriately and do not produce errors on valid inputs. Since thorough
testing is an integral part of the software engineering process, you are also provided
with an archived file tests.zip which contains 3 html test input files used to
evaluate assignment 4, together with the expected output csv representation. A
README file explains how to use them in your own evaluation and how to use
diff to compare your results with the provided expected output. The tests.zip
file is available on Connex in the assignment description.
7 What you must submit
• Python source-code name table_to_csv.py which contains your solution for
assignment #4.
• Ensure your work is committed to your local repository in the provided a4
folder and pushed to the remote before the due date/time. (You may
keep extra files used during development within the repository.)
8 Evaluation
The teaching staff will primarily mark solutions based on the input files provided for
this assignment, though additional files might also be used. Students must adhere to
the command execution and output formatting outlined in this assignment. There
will be no demos for this assignment.
In addition to automated testing, your code will be evaluated based on:
• Proper error handling
• Good coding practices (i.e. good variable/function naming, use of functions
when appropriate, limited globals, etc.)
Our grading scheme is relatively simple.
• ”A” grade: A submission completing ALL requirements of the assignment
with good code quality and all tests pass. The table_to_csv.py programs
runs without any problems.
• ”B” grade: A submission that completes the assignment and most tests pass.
The table_to_csv.py programs runs without any problems.
• ”C” grade: A submission that completes some parts of assignment and some
tests pass. The table_to_csv.py programs runs with some problems.
• ”D” grade: A serious attempt at completing requirements for the assignment.
The table_to_csv.py program compiles and runs with some problems.
• ”F” grade: Either no submission given; submission represents very little work
or understanding of the assignment.
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