Read the log file, search for keywords, print the first 5 lines of keywords. Yield, deque instances

From collections Import Deque

def search (lines, pattern, history=5):
    Previous_lines = deque (maxlen=history)
    For line in lines:
        If pattern in line:
            Yield Line,previous_lines
        Previous_lines.append (line)

if __name__ = = ' __main__ ':
    With open (' Log.txt ', ' R ', encoding= ' utf-8 ') as F:
        For line, prevlines in search (f, ' return ', 1):
            For Pline in Prevlines:
                Print (pline,end= ")
            Print (line,end= ")
            Print ('-' *20)

Read the log file, search for keywords, print the first 5 lines of keywords. Yield, deque instances