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<h3>File Input and Output</h3>
<p>The following program opens a file and reads its contents line by line:</p>
<PRE>
f = open("foo.txt") # Returns a file object
line = f.readline() # Invokes readline() method on file
while line:
print line, # trailing ',' omits newline character
line = f.readline()
f.close() </Pre>
<p>The <tT CLAss="monofont">open()</tt> function returns a new file object. By invoking methods on this object, you can perform various file operations. The <TT CLass="monofont">readline()</tt> method reads a single line of input, including the terminating newline. The empty string is returned at the end of the file. To make the output of a program go to a file, you can give the file to the <tt class="monofont">print</tt> statement using <tt clasS="monofont">>></tt> as shown in the following example:</P>
<pre>
f = open("out","w") # Open file for writing
while year <= numyears:
principal = principal*(1+rate)
print >>f,"%3d %0.2f" %% (year,principal)
year += 1
f.close() </Pre>
<p>In addition, files support a <tT claSS="monofont">write()</TT> method that can be used to write raw data. For example, the <tt clASS="monofont">print</Tt> statement in the previous example could have been written this way:</p>
<prE>
f.write("%3d %0.2f\n" % (year,principal)) </PRE>
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<P><TABLE width="100%" border=0><TR valign="top"><TD><font size=1 color="#C0C0C0"><br></font></TD><TD align=right><font size=1 color="#C0C0C0">Last updated on 3/28/2002<br>Python Essential Reference, Second Edition, © 2002 New Riders Publishing</font></TD></TR></TABLE></P>
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