Python basics: Every step with the yield keyword function call

1 #-*-coding:utf-8-*-2 __author__='Administrator'3 4  fromCollectionsImportdeque5 6 defSearch (lines, pattern, history=5):7Previons_line = Deque (maxlen=History )8      forLineinchlines:9         ifPatterninchLine :Ten             yieldLine , Previons_line One Previons_line.append (line) A  -  - #Example use on a file the if __name__=='__main__': -With open ('. \somefile.txt') as F: -          forLine, PrevlinesinchSearch (F,'python', 5): -              forPlineinchPrevlines: +                 Print(pline) -             Print(Line,"end= "") +             Print('-'*20) A            at      

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Contents of the Somefile.txt file:

The first call to the search () function returns to the main function when it runs to yield line,previons_line, that is, Previons_line is empty, which executes the output after the main function, and the second call to the search () function, directly from the Previons_ Line.append (line) starts running until the yield line,previons_line is run back to the main function. And so on, so the last line in Somefile.txt, "Python is end." Will not be added to the previons_line.

Python basics: Every step with the yield keyword function call