在显示控制台输入的同时，如何将输出写入文件？

Question

If I want to print the results of a python script or an other program to a file, I simple do something like this on the console python myscript.py>output.txt, but now myscript has an input inside and how can I get this to the console? For example I have script to check if a given year is a leap year or not:

def isLeapYear(year):
    return (year%4==0 and (year%400==0 or year%100!=0))

if __name__ == "__main__":
    y=input("Test if your year is a leap year: ")
    try:
        out=str(y)+" is"
        if not isLeapYear(int(y)):
              out+=" not";
        print(out+" a leap year")
    except ValueError:
        print("invaild input")

When I now write the command above, the result in my output-file is something like this (while I can just enter the year in the console):

Test if your year is a leap year: 2000 is a leap year

but I just want

2000 is a leap year

in there and have

Test if your year is a leap year:

shown on the console. Is there a clever way to do this? Can I somehow force print something to the console? Is there a general way to this? I mean I could have the same problem with a C or Java-Program.

Answer 1

According to the comments above:

*) You should handle the file writing in your python script, as we're in Python it's just a few lines of code.

*) About your question what would happen if someone still calls the script in the way that the output should be redirected, you can check in python if stdin and stdout are the same, if not the output got redirected according to Determining if stdout for a Python process is redirected

To safe you one more click here's the example code, test.py is a two-liner that does exactly this check:

    $ cat test.py
    import os
    print os.fstat(0) == os.fstat(1)
    $ python test.py
    True
    $ python test.py > f
    $ cat f
    False
    $

Hope that helps.

Cheers, Peter

Answer 2

If you want to keep the terminal printing I'd just edit the script to write the output.

outfile = open("leap-output.txt", "a+")

Then add the writing to the script.

outfile.write("%s a leap year") %(out)
outfile.write("\n")
outfile.close()

Redirecting the output with > is a bash function and you don't have a control over that.

As said by zvone you gain some control if you force users to give arguments the script ie.

userinput = sys.argv[1]

Then you'd start your script by typing python myscript.py example-output-file.txt

Python will crash here if user hasn't given the argument for the outfile.