How to Print Previous Row And Next Row In python List

Question

I want to print next and previous row , Here is my code

import csv
file= "myfile.txt"
searchname=input("Enter the name to be searched:")
f=open(file,'r')
reader=csv.reader(f)
lst=[]
for row in reader:
    lst.append(row)
    q=0
for row in lst:    
    if searchname in row:
        print(row)
        q+=1
    
f.close()

myfile.txt :

python,programming
java,programming
html,webdesigning
php,programming

I can Search "html" in python : The Output is ['html','webdesigning']
But I want to print
['java','programming']
['html','webdesigning']
['php','programming']

It is Possible?? Anyone Have an Answer?? pls help!

Python does come with some magic - well I mean nice tools - but at a time, you have to implement your logic. If you want to have a concept of rolling 3 rows you will have to implement it. You can use enumerate as a helper because it give you the current index, but beware: the first and last rows are corner cases. — Serge Ballesta
– Serge Ballesta, Commented Aug 20, 2020 at 12:26

TheFaultInOurStars · Accepted Answer · 2020-08-20 12:18:56Z

1

you can do this:

for index,row in enumerate(list):
if searchname in row:
    print(row)
    if index - 1 >= 0:
        print(list[index-1])
    if index + 1 < len(list):
        print(list[index+1])

answered Aug 20, 2020 at 12:18

TheFaultInOurStars

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1 Comment

KrisHnA Over a year ago

Thank You It Work

Orsiris de Jong · Accepted Answer · 2020-08-20 12:15:36Z

0

csv.reader provides a generator, so you can't just use it like a list. An easy way to achieve what you want should be to transform the reader object as list. You can then iterate over it, and when pattern is found, show the objects with current index -1, 0 and +1.

The try except statement handles the case where your found object is first or last.

import csv

file = "myfile.txt"
searchname = input("Enter the name to be searched:")
with open(file, 'r') as f:
    reader = list(csv.reader(f))
    for index, row in enumerate(reader):
        if searchname in row:
            for i in range(-1, 2):
                try:
                    print(reader[index+i])
                except IndexError:
                    pass

answered Aug 20, 2020 at 12:15

Orsiris de Jong

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1 Comment

Orsiris de Jong Over a year ago

May I know why this has been downvoted ? Should work perfectly and is accurate to the example given in the question.

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