Only use already existing files(python)

Question

Ok so I have a the name of a file as an raw input. But I the code to only use an already existing file and not and not be able to type in everything and just create new files.

So how can I make the program only use an already existing file and NOT create a new one if the input is wrong?

lista = {"police":"911"}
functiontext = raw_input("call function ")
arguments = raw_input("input file name ")

def save(lista,arguments):
     filen = arguments
     spara = lista
     fil = open(filen + ".txt","w")

for keys, values in spara.items():

        spara_content = keys + ": " + values + "\n"


        fil.write(spara_content)
        fil.close()

Answer 1

Consider using os.path.exists() or os.path.isfile() to test if the file is there. For example:

def save(lista,arguments):
    filen = arguments
    spara = lista
    fname = filen + ".txt"
    if os.path.isfile(fname):
        fil = open(filen + ".txt","w")
    else:
        print("The file {} does not exist, skipping".format(fname))