在两个方向上搜索一个行号的字符串

Question

使用Python 2.4，我正在阅读一个大的平面文件并选择一个特定的行号。现在我想在该行号之前搜索一个字符串，例如START，并在该行号之后搜索字符串END。

如何获取最近出现的字符串START（当前行号码前）和END（当前行号码后）的行号？

Answer 1

如何：

line_no = 1 

# Seek the last START before reaching the target line. 
start_line_no = -1 
while line_no != target_line_no: 
    line = input.readline() 
    if line == "": 
     # File is shorter than you think. 
     break 
    line_no += 1 
    if START in line: 
     start_line_no = line_no 

# Seek the first END after the target line.  
end_line_no = -1 
while true: 
    line = input.readline() 
    if line == "": 
     # END could not be found. 
     break 
    line_no += 1 
    if END in line: 
     end_line_no = line_no 
     break 

print start_line_no, end_line_no