TL;DR I need to get a user input that contains an argument in order to do something, I need my own script that gets user input, and acts like it's its own interpreter.
My goal is to make my own CLI with my own commands.
What I need now is to get user input within a python script. The grammar for my CLI is below: (The thing I don't know how to do)
COMMAND + ARGUMENT1 + ARGUMENT2 + ARGUMENT3
Example of what I want to do:
say "hi this is a test"
hi this is a test
I have a plan for how I can make the commands with arguments,
I make a folder named 'bin' and I put python scripts in them.
Inside the python scripts are functions.
Depending on the command type, either I call the functions do do something, or it prints a output.
But for now, I need to know HOW to get user input with ARGUMENTS
The built-in argparse module as #ToTheMax said can create complex command line interfaces.
By default argparse.ArgumentParser.parse_args() will read the command line arguments to your utility from sys.argv, but if you pass in an array, it will use it instead.
You can lex (split into an array of "words") a string just like the shell is using shlex.split() which is also built in. If you use quotation marks like in your example, the words between them won't be split apart, just as in the shell.
Here's a complete example. Refer to the documentation, because this is a bit of an advance usage of argparse. There is a section that talks about "subcommands" which is what this example is based on.
import argparse
import shlex
def do_say(args):
print(args.what)
parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers()
say_command = subparsers.add_parser('say')
say_command.add_argument('what')
say_command.set_defaults(func=do_say)
command = 'say "hi this is a test"'
args = parser.parse_args(shlex.split(command))
args.func(args)
The cmd module is another built-in way to make a command prompt, but it doesn't do the parsing for you, so you'd maybe combine it with argparse and shlex.
I realize I already have a question that is answered.
You can find it here:
How do you have an input statement with multiple arguments that are stored into a variable?
Here is the correct code:
def command_split(text:str) -> (str,str):
"""Split a string in a command and any optional arugments"""
text = text.strip() # basic sanitize input
space = text.find(' ')
if space > 0:
return text[:space],text[space+1:]
return text,None
x = input(":>")
command,args = command_split(x)
# print (f'command: "{command:}", args: "{args}"')
if command == 'echo':
if args == None:
raise SyntaxError
print (args)
A more simple way:
x = input(":>")
if x.split(" ")[0] == 'echo':
echoreturn = ' '.join(x.split(" ")[1:])
print(echoreturn)
My version to #rgov 's post: (Thank you!)
import argparse
import shlex
def do_say(args):
print(args.what)
parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers()
say_command = subparsers.add_parser('say')
say_command.add_argument('what')
say_command.set_defaults(func=do_say)
while True:
try:
command = input(":>")
args = parser.parse_args(shlex.split(command))
args.func(args)
except SyntaxError:
print("Syntax Error")
except ValueError:
print("Value Error")
except:
print("")
Related
#!/usr/bin/env python3
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--selection', '-s')
parser.add_argument('--choice', '-c', default = argparse.SUPPRESS)
args = parser.parse_args()
def main(selection, choice):
print(selection)
print(choice)
if __name__=='__main__':
main(args.selection, args.choice)
The example provided is just to provide something simple and short that accurately articulates the actual problem I am facing in my project. My goal is to be able to ignore an argument within the code body when it is NOT typed into the terminal. I would like to be able to do this through passing the argument as a parameter for a function. I based my code off of searching 'suppress' in the following link: https://docs.python.org/3/library/argparse.html
When I run the code as is with the terminal input looking like so: python3 stackquestion.py -s cheese, I receive the following error on the line where the function is called:
AttributeError: 'Namespace' object has no attribute 'choice'
I've tried adding the following parameter into parser like so:
parser = argparse.ArgumentParser(argument_default=argparse.SUPPRESS)
I've also tried the above with
parser.add_argument('--choice', '-c')
But I get the same issue on the same line.
#Barmar answered this question in the comments. Using 'default = None' in parser.add_argument works fine; The code runs without any errors. I selected the anser from #BorrajaX because it's a simple solution to my problem.
According to the docs:
Providing default=argparse.SUPPRESS causes no attribute to be added if the command-line argument was not present:
But you're still assuming it will be there by using it in the call to main:
main(args.selection, args.choice)
A suppressed argument won't be there (i.e. there won't be an args.choice in the arguments) unless the caller specifically called your script adding --choice="something". If this doesn't happen, args.choice doesn't exist.
If you really want to use SUPPRESS, you're going to have to check whether the argument is in the args Namespace by doing if 'choice' in args: and operate accordingly.
Another option (probably more common) can be using a specific... thing (normally the value None, which is what argparse uses by default, anyway) to be used as a default, and if args.choice is None, then assume it hasn't been provided by the user.
Maybe you could look at this the other way around: You want to ensure selection is provided and leave choice as optional?
You can try to set up the arguments like this:
parser = argparse.ArgumentParser()
parser.add_argument('--selection', '-s', required=True)
parser.add_argument('--choice', '-c')
args = parser.parse_args()
if __name__ == '__main__':
if args.choice is None:
print("No choice provided")
else:
print(f"Oh, the user provided choice and it's: {args.choice}")
print(f"And selection HAS TO BE THERE, right? {args.selection}")
I'm trying to parse commands with arguments using the python 3 Built-in argparse module.
I have read the argparse documentation partially, however, I could not find anything that meets my requirements.
I parse the arguments as input (I have my reasons).
I have multiple commands, for each, there are both essential and optional arguments.
For example:
restart --name (the name is replaced)
restart is the command and name is the essential argument.
Currently my code would count the "--" in the input and call the function with corresponding booleans (if --all given, is_all boolean parameter will be true)
I can also add an optional argument --all (all is not replaced).
Sounds like you are looking for something like this
def get_arguments():
parser = argparse.ArgumentParser()
parser.add_argument("--arg1", required=False, default=None)
parser.add_argument("--arg2", required=False, default=None)
return parser.parse_args()
args = get_arguments()
if args.arg1:
# do something
Really hard to answer this without seeing your code or example of what you want.
I'm assuming you're doing something like a shell of sorts. I'm going to also assume that each line entered has a command, each with their own arguments.
from argparse import ArgumentParser
def get_parser(cmd):
'''Returns a parser object for a given command'''
# Instantiate the parser object, add the appropriate arguments for the command
return parser # This is an example -- you need to instantiate it
def main():
while True:
try:
in_line = input('> ')
if not in_line.strip(): # Quit if empty
break
args = in_line.split()
parser = get_parser(args[0])
opts = parser.parser_args(args)
# Do stuff with opts depending on command
except EOFError:
break
except SystemExit:
pass # Prevent failures from killing the program by trapping sys.exit()
I currently have a python file that utilizes sys.argv[1] to accept a string at the command line. It then performs operations on that string and then returns the modified string to the command line.
I would like to implement a batch mode option in which I can provide a file of strings (one per line, fwiw) and have it return to the command line so that I can redirect the output doing something like
$ python script.py -someflag file.txt > modified.txt
while still retaining the current capabilities.
I am only running 2.6, so argparse is not an option. The tutorials I have seen either use argparse, getopt, or delve into examples that are too complex/don't apply.
What is the best way to check the input and act appropriately?
argparse is still an option, it's just not built into 2.6. You can still install it like any 3rd party package (for example, using easy_install argparse).
An example of code for this would be:
import sys
import argparse
p = argparse.ArgumentParser(description="script.py")
p.add_argument("-s", dest="string")
p.add_argument("-f", dest="infile")
args = p.parse_args()
if args.infile == None and args.string == None:
print "Must be given either a string or a file"
sys.exit(1)
if args.infile != None and args.string != None:
print "Must be given either a string or a file, not both"
sys.exit(1)
if args.infile:
# process the input file one string at a time
if args.string:
# process the single string
See my answer here: What's the best way to grab/parse command line arguments passed to a Python script?
As a shortcut, here's some sample code:
import optparse
parser = optparse.OptionParser()
parser.add_option('-q', '--query',
action="store", dest="query",
help="query string", default="spam")
options, args = parser.parse_args()
print 'Query string:', options.query
I have some scripts which do some processing on a file. Typically they accept the file as their first command-line argument, and other arguments after that.
I want to write a master script which accepts the name of the script to run, a wildcard specifying the target files (a-la glob), and possibly arguments to pass to the input script. The master script shall iterate over the files, and run the input script with the additional arguments.
Note that the input scripts are legacy, and possibly do not contain the usual if __name__ == "__main__": line at the end. They may also access sys.argv.
Any suggestions?
import glob
Should get you started,
I would also subprocess the scripts and pass them arguments.
You might try something like this. (very rough, but you get the idea)
import os
import sys
def callScripts(wildcard, arguments):
# convert a list ["hello", "world"] to a space delimited "hello world"
arguments = " ".join(arguments)
for file in os.listdir(".")
# feel free to replace with regex or w/e
if file.endswith(wildcard)
# system shell call
os.system("python " + file + " " + arguments)
if __name__ == "__main__":
wildcard = sys.argv[1]
arguments = sys.argv[2:]
callScripts(wildcard, arguments)
I am just starting with python so I am struggling with a quite simple example. Basically I want pass the name of an executable plus its input via the command line arguments, e.g.:
python myprogram refprogram.exe refinput.txt
That means when executing myprogram, it executes refprogram.exe and passes to it as argument refinput. I tried to do it the following way:
import sys, string, os
print sys.argv
res = os.system(sys.argv(1)) sys.argv(2)
print res
The error message that I get is:
res = os.system(sys.argv(1)) sys.argv(2)
^
SyntaxError: invalid syntax
Anyone an idea what I am doing wrong?
I am running Python 2.7
This line
res = os.system(sys.argv(1)) sys.argv(2)
Is wrong in a couple of ways.
First, sys.argv is a list, so you use square brackets to access its contents:
sys.argv[1]
sys.argv[2]
Second, you close out your parentheses on os.system too soon, and sys.argv(2) is left hanging off of the end of it. You want to move the closing parenthesis out to the very end of the line, after all of the arguments.
Third, you need to separate the arguments with commas, a simple space won't do.
Your final line should look like this:
res = os.system(sys.argv[1], sys.argv[2])
A far, far better way to do this is with the argparse library. The envoy wrapper library makes subprocess easier to work with as well.
A simple example:
import argparse
import envoy
def main(**kwargs):
for key, value in kwargs.iteritems():
print key, value
cmd = '{0} {1}'.format(kwargs['program'], ' '.join(kwargs['infiles']))
r = envoy.run(cmd)
print r.std_out
print r.std_err
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Get a program and run it with input', version='%(prog)s 1.0')
parser.add_argument('program', type=str, help='Program name')
parser.add_argument('infiles', nargs='+', type=str, help='Input text files')
parser.add_argument('--out', type=str, default='temp.txt', help='name of output file')
args = parser.parse_args()
main(**vars(args))
This reads in the arguments, parses them, then sends them to the main method as a dictionary of keywords and values. That lets you test your main method independently from your argument code, by passing in a preconstructed dictionary.
The main method prints out the keywords and values. Then it creates a command string, and passes that to envoy to run. Finally, it prints the output from the command.
If you have pip installed, envoy can be installed with pip install envoy. The easiest way to get pip is with the pip-installer.
sys.argv is a list, and is indexed using square brackets, e.g. sys.argv[1]. You may want to check len(sys.argv) before indexing it as well.
Also, if you wanted to pass parameters to os.system(), you might want something like os.system(' '.join(sys.argv[1:])), but this won't work for arguments with spaces. You're better off using the subprocess module.
sys.argv is a list
import sys, string, os
print sys.argv
res = os.system(sys.argv[1]) sys.argv[2]
print res
If you are running Python 2.7 it is recommended to use the new subprocess module.
In this case you would write
import sys, subprocess
result = subprocess.check_output(sys.argv[1], sys.argv[2])