Command-line usage tutorial for Assignments
In one or more of the questions in your assignments, you are required to input arguments to your program from the command line. Python provides the functionality to parse command-line options and arguments in multiple ways. The most common method is using sys.argv.
python programname.py argument1 argument2 argument3
python3 programname.py argument1 argument2 argument3
Example 1:
Consider a python program named program1.py that takes two files myfile1.txt and myfile2.txt as inputs to the program:
import sys
# this function reads a file and return its content
def read_file(file_path: str) -> str:
f = open(file_path, ‘r’)
line = f.readlines()
return line
if __name__ == ‘__main__’:
#retrieve the file paths from the commandline arguments
_, filename1, filename2 = sys.argv
print(“Number of arguments passed : “, len(sys.argv))
# since we know the program takes two arguments
print(“First argument : “, filename1)
print(“Second argument : “, filename2)
file1content = read_file(filename1)
print(“\nContent of first file : “, file1content)
file2content = read_file(filename2)
print(“\nContent of second file : “, file2content)
Here we use the terminal to run the python program.
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Example 2:
Consider a python program named program2.py that takes two files myfile1.txt and myfile2.txt as inputs to the program. Here we input the absolute paths to the two files in the command line.
import sys
# this function reads a file and return its content
def read_file(file_path: str) -> str:
f = open(file_path, ‘r’)
line = f.readlines()
return line
if __name__ == ‘__main__’:
print(“Number of arguments passed : “, len(sys.argv))
# this is the program name
print(“Oth argument : “, sys.argv[0])
# first argument/file path
print(“First argument : “, sys.argv[1]) # second argument/file path print(“Second argument : “, sys.argv[2])
print(“\nContent of first file : “, read_file(sys.argv[1]))
print(“\nContent of second file : “, read_file(sys.argv[2]))
Here we use the terminal to run the python program.
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Using PyCharm:
Select Edit configuration from the run tab in the menu list.
Type the file paths or arguments to your program in the text field next to parameters. Then press OK button.
Run your program.
Output of the program1.py is shown below.
The same procedure can be carried out to run the program2.py.
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