Issue reading csv file

问题

I am having trouble reading a saved csv with python:

import csv


with open('blah.csv','rb') as csvfile:
    data = csv.reader( csvfile )
    row_count = sum(1 for row in data)
    print row_count


    r = 1
    for row in data:
        print r

My issue is that although python seems to recognise the file and recognise that row_count = 9 (and prints this) it doesn't print r for each row in the later loop.

This code runs correctly on my computer, but not in the cloud on www.pythonanywhere.com

回答1:

That is because in the following line - row_count = sum(1 for row in data) - you have already read through the file and it has reached its end. So when you again try to do -

for row in data:
    print r

It would not work, because data file is at the end.

One of the many things you can try is re-openning the file again to read it from start.

Example -

import csv
with open('blah.csv','rb') as csvfile:
    data = csv.reader( csvfile )
    row_count = sum(1 for row in data)
    print row_count

with open('blah.csv','rb') as csvfile:
    data = csv.reader( csvfile )
    r = 1
    for row in data:
        print r

Though you can also make both counting of lines and printing the line into a single loop like -

import csv
with open('blah.csv','rb') as csvfile:
    data = csv.reader( csvfile )
    row_count = 0
    for row in data
        row_count += 1
        print row
    print row_count

Another thing you can do is -

csvfile.seek(0) #to make the file point to the start.

Example -

import csv
with open('blah.csv','rb') as csvfile:
    data = csv.reader( csvfile )
    row_count = sum(1 for row in data)
    print row_count
    csvfile.seek(0)
    r = 1
    for row in data:
        print r

来源：https://stackoverflow.com/questions/31367594/issue-reading-csv-file