Python: How to parse places in place? -


does not have headers several columns such:

john, 1, orange, chicken mary, 7, purple, hamburger joey, 2, yellow, chicken

you don't need csv this, simple python. solution efficient regards memory, operates row row.

with open('temp.csv', 'r') fin, open('temp2.csv', 'w') fout:     row in fin:         if row.split()[3] == 'chicken':             fout.write(row)

this more memory efficient list comprehension requires reading , storing in memory data written file out.

timings

# create sample data file of 30k rows, 2/3rds 'chicken'. open('temp.csv', 'w') f:     _ in range(10000):         f.write("john,1,orange,chicken\n")         f.write("mary,7,purple,hamburger\n")         f.write("joey,2,yellow,chicken\n")  %%timeit open('temp.csv', 'r') fin, open('temp2.csv', 'w') fout:     row in fin:         if row.split()[3] == 'chicken':             fout.write(row) # 10 loops, best of 3: 41 ms per loop  %%timeit open('temp.csv') old_file, open('temp3.csv', 'w') new_file:     cr = csv.reader(old_file)     cw = csv.writer(new_file)     cw.writerows([r r in cr if r[3] == 'chicken']) # 10 loops, best of 3: 58.7 ms per loop  # turn previous list comprehension generator. %%timeit open('temp.csv') old_file, open('temp3.csv', 'w') new_file:     cr = csv.reader(old_file)     cw = csv.writer(new_file)     cw.writerows((r r in cr if r[3] == 'chicken')) # 10 loops, best of 3: 66.5 ms per loop  open('temp.csv') input_file, open('temp4.csv', 'w', newline='') output_file:     reader = csv.reader(input_file, delimiter=',')     writer = csv.writer(output_file, delimiter=',')     writer.writerows(filter(lambda x: x[3].strip() != 'chcicken', reader)) --------------------------------------------------------------------------- typeerror                                 traceback (most recent call last) <ipython-input-41-072d37a3ff92> in <module>() ----> 1 open('temp.csv') input_file, open('temp4.csv', 'w', newline='') output_file:       2     reader = csv.reader(input_file, delimiter=',')       3     writer = csv.writer(output_file, delimiter=',')       4     writer.writerows(filter(lambda x: x[3].strip() != 'chcicken', reader))  typeerror: 'newline' invalid keyword argument function

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