Python processing csv file

Question

I am encountering some weird things here.I am using python's csv module to process csv file. The example code is below

import csv
f = open('file.csv','r')
for i in csv.reader(f):
    print i

This prints out all rows as lists and works just fine.And then when I want to do another thing like

for i in csv.DictReader(f):
    print i['header']

Think this should print all the data with the header called 'header'.It failed.Then I tried a lot.I found I need to run the open file function again each time I run some csv method.It seems redundant to me.Think i might miss some steps.

yelsayed · Accepted Answer · 2016-11-17 06:46:46Z

3

When you're done reading the file the first time, you need to seek back to its beginning to read it again. Something like f.seek(0,0).

answered Nov 17, 2016 at 6:46

yelsayed

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4 Comments

Philipl Over a year ago

Oh!thanks!Does it means the reader has some point like thing exists?

yelsayed Over a year ago

Not sure what you mean @honesty1997. File objects remember file offset they last worked with, so if you need to interact with a file multiple times using the same file object (f in this example), make sure to reset that location to the beginning.

Philipl Over a year ago

Thanks!Does it means that in this case after I looped through the file, the next time I wanted to loop it again and got nothing because that the file object remember that last time I loop through the file and stop at the end of the object?

yelsayed Over a year ago

You got it @honesty1997.

kvivek · Accepted Answer · 2016-11-17 07:09:29Z

0

You can try like this way to only get the headers.

import csv
f = open('file.csv')
csvDictInstance = csv.DictReader(f)
print csvDictInstance.fieldnames

answered Nov 17, 2016 at 7:09

kvivek

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