This question already has answers here:
How to read/process command line arguments?
(22 answers)
Closed 7 years ago.
I'm reading an online book on Python.It mentioned command line arguments,but I don't know what they are? Can anybody explain them for me with an example?
I don't know what your level of programming experience is, but command line arguments are a pretty common thing. In the olden days, every program you created was done in a text editor, and then run on a command line.
The command line is, in simple terms, a program built into the operating system which allows you to run programs by calling them by name. In Windows, this command line is called the Command Prompt. On other operating systems, it is usually called Terminal.
Though you may be familiar with running programs through an IDE, you can also run them from the command line. To run a python program, you could type:
python the_program.py
to run a program, assuming you have python installed and your terminal knows where it is. So command line arguments are a sort of variable/argument you send to a program that is run this way. If you say:
python the_program.py 100 hello 3.35
You can access these values from within your program, by adding
import sys
to the top, and in the body of your code by accessing the array of arguments, named
sys.argv
Command line argument are all addition information passed to the script after the name of the script.
Is you run a python script like:
python myscript.py abc 123
Then abc 123 are the command line arguments. They can be accessed in Python as a list as sys.argv.
Related
I had a python file named abc.py which accepts two command line arguments. To run the the code I will have to type
python abc.py 3 5
But I want something like this (neither the python keyword nor the python extension),
abc 3 5
Note: I don't want to run like this - ./abc.
This question has already been asked in how to make a python file run without py extension but I cant find any helpful answer. Could someone help me ?
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Running a python script from the command line in Windows
(3 answers)
Closed 6 years ago.
I have pycharm installed and do my class assignment in it and things work well. The teacher wants on to now run some of the programs in command prompt. Given that my programs and the path is here: "C:\Python27\python.exe C:/Users/sz5062/PycharmProjects/untitled1/main.py", how can I run a program that is saved the above path in command line? So, example, how would I run the main.py in command line, not shell prompt?
I have searched and searched for answers here, but I can't fine one. Thanks very much for your help.
This is the full instruction: Install Python and a programming text editor and write a program that prints one line other than 'hello world', then take two screen shots and upload them below. You should use the command line to execute the Python program you wrote in the text editor. Please do not use the IDLE Python Shell, the Python Interpreter (>>>), or a shortcut in your text editor to run the code.
When i run "python main.py", I get an error message "python is not recognized as inernal or external command".
On you Commandline enter:
C:\Python27\python.exe C:\Users\sz5062\PycharmProjects\untitled1\main.py
The above command should work from every directory.
First part is the program you start (python.exe). Second part is the argument you pass to the program(C:\Users\sz5062\PycharmProjects\untitled1\main.py). This is the path to your python code so that python.exe knows what you want to execute.
If you add C:\Python27\ to your PATH variable, you can navigate to your directory C:\Users\sz5062\PycharmProjects\untitled1\ and start your programm with:
python main.py
I'd recommend making sure that python is on your PATH (if you type python does it open a shell?) and then navigate to the C:/Users/sz5062/PycharmProjects/untitled1 directory. Once there you can do:
python main.py
and that should work.
I think I made this hard. since python was in installed on C:\python27, all I needed to run the command line was simply to write the code in a text editor, save it in the same directory and call it from there. So, essentially, c:\python27\code.py
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Why do people write #!/usr/bin/env python on the first line of a Python script?
(22 answers)
Closed 7 years ago.
Okay I am new to Python, but my code does not run if the line
#!/usr/bin/python
is not present at the beginning of the file. Why is that ? What does it mean ? I thought it was used for to denote a python version if there were multiple versions installed.
#!/usr/bin/python
def main():
a = [1,2,3]
print a
if __name__ == "__main__":
main()
Omitting the #!/usr/bin/python gives the following error only if I execute it using
./test.py on Ubuntu
if however I use the python command to run then it runs fine without the /usr/bin line.
The first line of the script beginning with #! is a shebang (sometimes called a hash-bang).
The following executable path denotes which interpreter should be used to process the following code (in your case, /usr/bin/python).
If you run the script from the shell with python test.py, you don't need a shebang - the executable is python and the script is passed to it as an argument.
In Unix you can tell a file how it should be opened if it contains a script language (in your case Python).
This line is known as Shebang.
./filename is used to run executable files, to execute it you need to specify the application required.
Whereas, in using python filename.py you already specify the application to use that is python in this case.
This question already has answers here:
How to read/process command line arguments?
(22 answers)
Closed 8 years ago.
I wrote a code using Python in Geany within windows and I'm using arguments in the code. I execute the program within the Geany so I don't know how to use arguments.
How could I convert the program to be be run as a standalone system, not to be run from within an IDE.
how could I use terminal in windows to run the code like this :
John~/home/args -> ./test.py -h
In Notepad, write what you would in terminal...
python test.py -h
Save it as a .bat file... Then you can run the bat file :)
PS. This goes for anything you wish to run in CMD
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Why do people write #!/usr/bin/env python on the first line of a Python script?
What does the line “#!/bin/sh” mean in a UNIX shell script?
It's a comment and should be ignored by the interpreter. Why is #!/usr/bin/python still in almost every program?
If the script is made executable, the operating system will use that first line to know which interpreter to run to parse the rest of the file to perform some action.
If you always run these kinds of scripts from the command line like python foo.py then you could remove the first line.
Not actually. It is tradition in Unix like operating systems to use the interpreter path given in the first line and use the path to that interpreter for interpreting the rest of the program. It is called as Shebang line. You would not cared for it if you were not on Unix like systems (linux. Mac OS, FreeBSD etc) but there are attempts in Python community to use similar shebang lines on windows too.
Read the Wikipedia article Shebang. Also remember outside the *nix world, the first shebang prefixed line is considered as a comment.