Python搜索文本文件，在字符串后打印字符

Question

我希望能夠在文檔中搜索給定的字符串並找到每個實例的上下文。 例如，在文檔中搜索“ Figure”，然后在該字符串后返回X個字符（從“ Figure-1 Super awesome Figure。next句話”中返回“ -1 Super awesome Figure”。）

我知道如何打印：A）該字符串的每個實例

mystring = "Figure"
with open('./mytext.txt', 'r') as searchfile:
    for line in searchfile:
        if mystring in line:
            print(mystring)

但這沒有幫助； 或B）包含該字符串的每一行

for line in open('./mytext.txt', "r"):
    if "Figure" in line:
        print(line) 

它返回整行之前和之后的所有文本，這對我來說很麻煩。

我可以在“ mystring”處分割一行並在分割后返回X個字符嗎？ 還是有一個更好的方法？

Answer 1

我會這樣做：

WANTED = 20 #or however many characters you want after 'Figure'

with open('mytext.txt') as searchfile:
    for line in searchfile:
        left,sep,right = line.partition('Figure')
        if sep: # True iff 'Figure' in line
            print(right[:WANTED])

請參閱： str.partition

Answer 2

您可以執行以下操作：

line = "Figure-1 Super awesome figure. next sentence."

search_line = line.split("Figure")

print search_line

# prints ['', '-1 Super awesome figure. next sentence.']

count = 0
for elem in search_line: 
    count += len(elem)

print count # how many chars after "Figure"

Answer 3

import re
X = len("-1 Super awesome figure")
regex = re.compile("Figure.{%d}" % X)
for line in open("mytext.txt"):
  for m in regex.findall(line):
    print m

您可能需要澄清“返回該字符串后的X個字符”的含義。