How to loop through a specific range of rows with Python csv reader?
The following code loops through all rows:
with open(trainFile, 'rt') as csvfile:
spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
for row in spamreader:
print (', '.join(row))
I wish to loop only from given (i to j).
You can use itertools.islice:
import itertools
i, j = 10, 20
with open(trainFile, 'rt') as csvfile:
spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
for row in itertools.islice(spamreader, i, j+1):
print (', '.join(row))
Alternative (following code is possible because csv.reader accept an iterable):
NOTE: only works when CSV rows do not contain newline.
import itertools
i, j = 10, 20
with open(trainFile, 'rt') as csvfile:
spamreader = csv.reader(itertools.islice(csvfile, i, j+1),
delimiter=' ', quotechar='|')
for row in spamreader:
print (', '.join(row))
Use islice, eg:
rows_1_to_50 = itertools.islice(spamreader, 0, 50)
for row in rows_1_to_50:
pass
Another itertools implementation using dropwhile and takewhile
from itertools import takewhile, dropwhile
trainFile = 'x.1'
low_lim = 3
high_lim = 6
with open(trainFile, 'rt') as csvfile:
spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
g = (x for x in enumerate(spamreader, 1))
g = dropwhile(lambda x: x[0] < low_lim, g)
g = takewhile(lambda x: x[0] <= high_lim, g)
for row in g:
print (', '.join(row[1]))
trainFile = 'x.1' that refers to the complete path, correct?