2013年8月12日Python的5个最有价值问题

问:Python怎么在字典里删除值但保留相应的键

答:

假设3都在值里,而非键
>>> for v in D1.values():
...     if 3 in v:
...         v.remove(3)
...
>>> D1
{'A1': [2], 'C1': [4, 5], 'B1': [3]}

这个代码还能适用于更多情况,比如:
>>> D1 = {'A1' : [2, 3], 'B1': [3, 3], 'C1' : [4, 5]}
>>> for k, v in D1.items():
...     D1[k] = filter(lambda x: x!=3, v)
...
>>> D1
{'A1': [2], 'C1': [4, 5], 'B1': []}

问:Python的TKinter框架怎么创建实体表

答:

from Tkinter import *

from string import ascii_lowercase

  

class app(Frame):

    def __init__(self, master = None):

        Frame.__init__(self, master)

        self.grid()

        self.create_widgets()

  

    def create_widgets(self):

        self.entries = {}

        self.tableheight = 9

        self.tablewidth = 9

        counter = 0

        for row in xrange(self.tableheight):

            for column in xrange(self.tablewidth):

                self.entries[counter] = Entry(self, width=5)

                self.entries[counter].grid(row=row, column=column)

                counter += 1

  

prog = app()

prog.master.title('Sudoku')

prog.mainloop()

 

问:Python怎么转换Dictionary为DataFrame?

答:

import json

import pandas as pd

  

db = json.loads(open('pruItems.json', 'r').read())

pieces = []

for d in db:

    if d['data']:

        df = pd.DataFrame(d['data'])

        df.columns = ['date', 'bid', 'ask']

        df = df.set_index('date')

        pieces.append(df)

  

df = pd.concat(pieces, axis=1, keys=[d['fund'] for d in db])

  

print df

输出:

                TGC               FEF              FAF       

                bid      ask      bid      ask     bid     ask

date                                                         

18/06/2013  34.8400  34.8400  14.9179  14.9179  6.6780  6.6780

17/06/2013  34.4900  34.4900  14.8712  14.8712  6.6510  6.6570

 

问:Python怎么使用BeautifulSoup来提取两个Html标签之间的内容

答:

使用.content

>>> from bs4 import BeautifulSoup as BS

>>> html = """<li class="li_dataline2">

...

...

... <b> Expiry date: </b>14/09/2013

...

...

... </li>"""

>>> soup = BS(html)

>>> print soup.find('li', {'class':'li_dataline2'}).contents[-1].strip()

14/09/2013