Iterate File
Lesson: Iterate file
Create a Python script that
- takes a file name/path as a command line argument
- opens a file using the built-in
open()function - uses a generator to iterate over the file's lines and
- yields these lines split by the ','-separator character and
- prints them to stdout (i.e. the console)
Optional: Add a command line option that allows for setting the separator to another character.
Optional 2: Add command line options to set an output file path and write the processed lines to this output file, joining the split lines with another "target separator" (also set with a command line option).
Use the argparse stdlib library to parse the command line (see https://docs.python.org/3/howto/argparse.html).
Example `iterate_file.py
iterate_file.py
""" iterate_file"""
import argparse
# https://docs.python.org/3/howto/argparse.html
def gen(lines, separator=','):
'''generator function'''
for line in lines:
for _line in line.split(separator):
yield _line
def main(args):
if not args.input_file: # optional-argument
input_file = input("input_file: ")
else:
input_file = args.input_file
with open(input_file) as my_input_file:
if args.output_file:
if args.output_separator:
out_separator = args.output_separator
else:
out_separator = "\n"
with open(args.output_file, 'w') as my_output_file:
# readlines(): Read the whole file at once
# returns a list of lines
for line in gen(my_input_file.readlines()):
# rstrip(): removes trailing whitespaces and newlines
my_output_file.write(line.rstrip()+ out_separator)
else:
# No output_file given, so just print to stdout
for line in gen(my_input_file.readlines()):
# rstrip(): removes trailing whitespaces and newlines
print(line.rstrip())
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('--input_file', help='Path to file"')
parser.add_argument('--input_separator', help='line separator of input file')
parser.add_argument('--output_file', help='Path to file"')
parser.add_argument('--output_separator', help='line separator of output file')
args = parser.parse_args()
main(args)
The Python Script can be called as shown in the shell one-liners: