擅长:python、mysql、java
<p>如果先计算-eval()-PI字符串,然后通过str()命令将计算结果作为str插入str1,然后计算str1,会怎么样</p>
<pre><code>from math import *
PI = "1*pi"
str1 = "2*PI"
PI = str(eval(PI)) # Turns our PI string into a number
str1 = str1.replace("PI",PI) # Sets our PI number in
print(eval(str1)) # Calculates it one last time
</code></pre>
<p><strong>输出</strong></p>
<pre><code>6.283185307179586
</code></pre>