>>> f=open('p.txt','w') # open for writing >>> dir(f) ['close', 'closed', 'fileno', 'flush', 'isatty', 'mode', 'name', 'read', 'readinto', 'readline', 'readlines', 'seek', 'softspace', 'tell', 'truncate', 'write', 'writelines', 'xreadlines'] >>> f.write('first line\n') >>> f.write('second line\n') >>> f.close() # close file >>> f=open('p.txt','r') # open for reading >>> for line in f.readlines(): ... print line ... first line second line >>> f.close() # close file >>> f=open('p.txt','a') # open appending >>> f.write('new line with a number ' + str(12.25)+'\n') >>> f.close() >>> f=open('p.txt','r') # open for reading >>> for line in f.readlines(): ... print line ... first line second line new line with a number 12.25Di solito, specialmente per i file, è utile sapere se il file che stiamo tentando di aprire esiste, al fine di non proseguire in caso di errore. A tale scopo usiamo il costrutto try: except:, come nel caso
>>> f=open('p1.txt','r') # open for reading Traceback (most recent call last): File "<stdin>", line 1, in ? IOError: [Errno 2] No such file or directory: 'p1.txt' >>> def test_open_file(filename,mode): # define a test function ... try: ... f=open(filename,mode) ... except: ... f=None ... print 'Error in file ',filename,'with mode',mode ... return f ... >>> f=test_open_file('p.txt','r') >>> f <open file 'p.txt', mode 'r' at 0x810f138> >>> f.close() >>> f=test_open_file('p1.txt','r') Error in file p1.txt with mode r >>> f >>>Per un più approfondito utilizzo dei file si rimanda a www.python.org/doc/.