读出基于文本文件的字典的定义

Question

I'm trying to write a Python function that takes as an input a text file based dictionary, for example Webster's free dictionary. The function "webster_definition" will then search through the text file and print the definition for a specific word, eg "Canada".

Here is what I've got so far:

import re
import sys

def webster_definition(word):
    word = word.upper()
    output = ""
    doc = open("webster.txt",'r')           

    for line in doc:     
        if re.match(word,line):
            print line

    return output

print webster_definition("Canada")

This will output the word I looked for. But the definition starts three lines later with "Defn:" and is of variable length, eg:

CANADA
Can"a*da, n.

Defn: A British province in North America, giving its name to various
plants and animals. Canada balsam. See under Balsam.
 -- Canada goose. (Zoöl.) See Whisky Jack.
 -- Canada lynx. (Zoöl.) See Lynx.
 -- Canada porcupine (Zoöl.) See Porcupine, and Urson.
 -- Canada rice (Bot.) See under Rick.
 -- Canada robin (Zoöl.), the cedar bird.

The desired output should look like:

CANADA
Defn: A British province in North America, giving its name to various
plants and animals. Canada balsam. See under Balsam.
 -- Canada goose. (Zoöl.) See Whisky Jack.
 -- Canada lynx. (Zoöl.) See Lynx.
 -- Canada porcupine (Zoöl.) See Porcupine, and Urson.
 -- Canada rice (Bot.) See under Rick.
 -- Canada robin (Zoöl.), the cedar bird.

Can anyone help me with the output of the definition?

Answer 1

in file:

CANADA
Can"a*da, n.

Defn: A British province in North America, giving its name to various
plants and animals. Canada balsam. See under Balsam.
 -- Canada goose. (Zoöl.) See Whisky Jack.
 -- Canada lynx. (Zoöl.) See Lynx.
 -- Canada porcupine (Zoöl.) See Porcupine, and Urson.
 -- Canada rice (Bot.) See under Rick.
 -- Canada robin (Zoöl.), the cedar bird.

 ANOTHER DEFENITION
 another defenition

 Defn.. some words
 more words
 ......


with open('webster_file', 'r') as f:
     # read into a string.
     data = f.read()

# uppercase word to search for
word = 'canada'.upper()
# search for empty line and the get everything non-greedy up to the 
# another empty line.
pattern = '^' + word + '.*?\n^$\n.*?^$'

mo = re.search(pattern,data,re.M|re.DOTALL)

if mo:
    print(mo.group(0))


CANADA
Can"a*da, n.

Defn: A British province in North America, giving its name to various
plants and animals. Canada balsam. See under Balsam.
 -- Canada goose. (Zoöl.) See Whisky Jack.
 -- Canada lynx. (Zoöl.) See Lynx.
 -- Canada porcupine (Zoöl.) See Porcupine, and Urson.
 -- Canada rice (Bot.) See under Rick.
 -- Canada robin (Zoöl.), the cedar bird

Answer 2

I am not sure i completely follow.

But if you do not want to print empty lines you can check for it and not print them, eg:

if line in ['\n', '\r\n', '']:
    continue
print line

Answer 3

# coding: utf-8

data = '''CANADA
Can"a*da, n.

Defn: A British province in North America, giving its name to various
plants and animals. Canada balsam. See under Balsam.
 -- Canada goose. (Zoöl.) See Whisky Jack.
 -- Canada lynx. (Zoöl.) See Lynx.
 -- Canada porcupine (Zoöl.) See Porcupine, and Urson.
 -- Canada rice (Bot.) See under Rick.
 -- Canada robin (Zoöl.), the cedar bird.'''

data = data.split('\n\n')
data = [data[0].split('\n')[0]] + [data[1]]
data = '\n'.join(data)

Answer 4

It usually helps to decompose the task into simpler functions. For the case of text files parsing, generators are very handy:

def read_paragraph(fp):
    """ 
    Read lines from the file until the end of the paragraph 
    """
    while True:
        line = fp.readline()
        if not line.strip():
            break
        yield line

def skip_paragraph(fp):
    while fp.readline().strip():
        pass

def find_definition(fp, word):
    word = word.upper()
    while True:
        line = fp.readline()
        if not line:
            break  # end of file, consider raising an exception here

        if line.strip() == word:
            yield line          # found the word
            skip_paragraph(fp)  # move to the definition
            for defline in read_paragraph(fp):
                yield defline
            break
        else:
            # we're not interested in the current word, just skipping it
            skip_paragraph(fp)
            skip_paragraph(fp)

Finally, to get a definition:

with open('webster.txt') as fp:
    definition = find_definition(fp, 'Canada')
    print ''.join(definition)

That said, if you need to query the dictionary often, and performance is of any concern, consider converting the text file into an sqlite database.