美丽的汤代码会带来意想不到的结果（已编辑）

Question

(The question was edited based on feedback received. I will continue to edit it based on input received until the issue is resolved)

I am learning Pyhton and beautiful soup in particular and I am doing the Google Exercise on Regex using the set of html files that contains popular baby names for different years (eg baby1990.html etc). You can find this dataset if you are interested here: https://developers.google.com/edu/python/exercises/baby-names

Each html file contains a table with baby names data that looks like this:

Before the table with the baby names there is another table. The html code in the Tags of the two tables is respectively the following

<table width="100%" border="0" cellspacing="0" cellpadding="4"> # Unwanted table
<table width="100%" border="0" cellspacing="0" cellpadding="4" summary="formatting">  # targeted table

You may observe that the targeted differs from the unwanted table by the attribute: summary="formatting"

The first table--the one we must skip -- has the following html code:

<table width="100%" border="0" cellspacing="0" cellpadding="4">
  <tbody>
  <tr><td class="sstop" valign="bottom" align="left" width="25%">
      Social Security Online
    </td><td valign="bottom" class="titletext">
      <!-- sitetitle -->Popular Baby Names
    </td>
  </tr>
  <tr bgcolor="#333366"><td colspan="2" height="2"></td></tr>
  <tr><td class="graystars" width="25%" valign="top">
       <a href="../OACT/babynames/">Popular Baby Names</a></td><td valign="top"> 
      <a href="http://www.ssa.gov/"><img src="/templateimages/tinylogo.gif"
      width="52" height="47" align="left"
      alt="SSA logo: link to Social Security home page" border="0"></a><a name="content"></a>
      <h1>Popular Names by Birth Year</h1>September 12, 2007</td>
  </tr>
  <tr bgcolor="#333366"><td colspan="2" height="1"></td></tr>
</tbody></table>

Within the targeted table the code is the following:

<table width="100%" border="0" cellspacing="0" cellpadding="4" summary="formatting">
<tr valign="top"><td width="25%" class="greycell">
<a href="../OACT/babynames/background.html">Background information</a>
<p><br />
&nbsp; Select another <label for="yob">year of birth</label>?<br />      
<form method="post" action="/cgi-bin/popularnames.cgi">
&nbsp; <input type="text" name="year" id="yob" size="4" value="1990">
<input type="hidden" name="top" value="1000">
<input type="hidden" name="number" value="">
&nbsp; <input type="submit" value="   Go  "></form>
</td><td>
<h3 align="center">Popularity in 1990</h3>
<p align="center">
<table width="48%" border="1" bordercolor="#aaabbb"
 cellpadding="2" cellspacing="0" summary="Popularity for top 1000">
<tr align="center" valign="bottom">
<th scope="col" width="12%" bgcolor="#efefef">Rank</th>
<th scope="col" width="41%" bgcolor="#99ccff">Male name</th>
<th scope="col" bgcolor="pink" width="41%">Female name</th></tr>
<tr align="right"><td>1</td><td>Michael</td><td>Jessica</td> # Targeted row
<tr align="right"><td>2</td><td>Christopher</td><td>Ashley</td> # Targeted row
etc...

You can see that the distinctive attribute of the targeted rows is: align = "right".

Now the code to extract the content of the targeted cells is the following:

with open("C:/Users/ALEX/MyFiles/JUPYTER NOTEBOOKS/google-python-exercises/babynames/baby1990.html","r") \
as f: soup = bs(f.read(), 'html.parser') 

print soup.tr
print "number of elemenents in the soup:" , len(soup)

right_table = soup.find("table", summary = "formatting")

print(right_table.prettify())

print "right_table" , len(right_table)

print(right_table[0].prettify())

for row in right_table[1].find_all("tr", allign = "right"):

     cells = row.find_all("td")

     try:
                            print "cells[0]: " , cells[0]
     except:
                            print "cells[0] : NaN"
     try:
                            print "cells[1]: " , cells[1]
     except:
                            print "cells[1] : NaN"    
     try:
                            print "cells[2]: " , cells[2]
     except:
                            print "cells[2] : NaN"

The output is an error message:

    <tr><td align="left" class="sstop" valign="bottom" width="25%">
      Social Security Online
    </td><td class="titletext" valign="bottom">
<!-- sitetitle -->Popular Baby Names
    </td>
</tr>
number of elemenents in the soup: 4
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-116-3ec77a65b5ad> in <module>()
      6 right_table = soup.find("table", summary = "formatting")
      7 
----> 8 print(right_table.prettify())
      9 
     10 print "right_table" , len(right_table)

C:\users\alex\Anaconda2\lib\site-packages\bs4\element.pyc in prettify(self, encoding, formatter)
   1198     def prettify(self, encoding=None, formatter="minimal"):
   1199         if encoding is None:
-> 1200             return self.decode(True, formatter=formatter)
   1201         else:
   1202             return self.encode(encoding, True, formatter=formatter)

C:\users\alex\Anaconda2\lib\site-packages\bs4\element.pyc in decode(self, indent_level, eventual_encoding, formatter)
   1164             indent_contents = None
   1165         contents = self.decode_contents(
-> 1166             indent_contents, eventual_encoding, formatter)
   1167 
   1168         if self.hidden:

C:\users\alex\Anaconda2\lib\site-packages\bs4\element.pyc in decode_contents(self, indent_level, eventual_encoding, formatter)
   1233             elif isinstance(c, Tag):
   1234                 s.append(c.decode(indent_level, eventual_encoding,
-> 1235                                   formatter))
   1236             if text and indent_level and not self.name == 'pre':
   1237                 text = text.strip()

... last 2 frames repeated, from the frame below ...

C:\users\alex\Anaconda2\lib\site-packages\bs4\element.pyc in decode(self, indent_level, eventual_encoding, formatter)
   1164             indent_contents = None
   1165         contents = self.decode_contents(
-> 1166             indent_contents, eventual_encoding, formatter)
   1167 
   1168         if self.hidden:

RuntimeError: maximum recursion depth exceeded while calling a Python object

The questions are the following:

1. Why the code returns the first table -- the unwanted one-- given that we have passed the argument summary = "formatting"?

2. What the error message implies? Why it is created?

3. What are other errors you can observe in the code -- if any?

Your advice will be appreciated.

Answer 1

I think you're misreading the attribute searching.

If you're looking for 'has summary equal to "Popularity for top 1000"', you should use:

soup.find('table', summary="Popularity for top 1000")

Hopefully that works for you!

Answer 2

summary_ = "formatting"
allign_ = "right"

delete the _ , only class_ has _ .

It's very useful to search for a tag that has a certain CSS class, but the name of the CSS attribute, “ class ”, is a reserved word in Python. Using class as a keyword argument will give you a syntax error. As of Beautiful Soup 4.1.2, you can search by CSS class using the keyword argument class_

with open('/home/li/Downloads/google-python-exercises/babynames/baby2006.html') as f:
    soup = bs4.BeautifulSoup(f, 'lxml')
    table = soup.find(summary="Popularity for top 1000")
    for tr in table.find_all('tr'):
        tds = list(tr.stripped_strings)
        print(tds)

out:

['Rank', 'Male name', 'Female name']
['1', 'Jacob', 'Emily']
['2', 'Michael', 'Emma']
['3', 'Joshua', 'Madison']
['4', 'Ethan', 'Isabella']
['5', 'Matthew', 'Ava']
['6', 'Daniel', 'Abigail']
['7', 'Christopher', 'Olivia']
['8', 'Andrew', 'Hannah']
['9', 'Anthony', 'Sophia']
['10', 'William', 'Samantha']
['11', 'Joseph', 'Elizabeth']