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<p>我写了下面的代码,但replace方法不起作用</p>
<p>代码:</p>
<pre><code>courses = input("Please enter the courses you have taken previously with letter grades: ")
courses.replace("M","X")
print(courses)
</code></pre>
<p>请以字母成绩输入您之前所修的课程:</p>
<pre><code>MATH101:A;SPS101:B;CS201:B+;HIST191:D;CS204:F;CS210:S:
MATH101:A;SPS101:B;CS201:B+;HIST191:D;CS204:F;CS210:S:
</code></pre>