python name 'file' is not defined的解决办法

源码：

poem = '''\
Programming is fun
When the work is done
if you wanna make your work also fun:
        use Python!
'''

f = file('poem.txt', 'w') # open for 'w'riting
f.write(poem) # write text to file
f.close() # close the file

f = file('poem.txt')
# if no mode is specified, 'r'ead mode is assumed by default
while True:
    line = f.readline()
    if len(line) == 0: # Zero length indicates EOF
        break
    print (line),
    # Notice comma to avoid automatic newline added by Python
f.close() # close the file

错误提示：

Traceback (most recent call last):
File "C:/Python31/004.py", line 8, in <module>
    f = file('poem.txt', 'w') # open for 'w'riting
NameError: name 'file' is not defined

解决办法：file()改为open()