<P>考虑如下:</P>
<pre><code>a = 1
a = +1 # Assign Var a to value -> +1
a = +1 # Assign Var a to value -> +1
a = +1 # Assign Var a to value -> +1
a += 1
a += 1
a += 1
print(a) # -> 4
</code></pre>
<p>正如您所看到的<code>a = +1</code>它是一个<a href="https://www.w3schools.com/python/python_variables.asp" rel="nofollow noreferrer">variable assignment</a>(由@adir abargil更正),但是<code>a += 1</code>确实将1添加到var<code>a</code></p>
<p>这与a=a+1相同,称为:<strong>赋值运算符</strong></p>
<hr/>
<h2>其他堆栈溢出答案</h2>
<ul>
<li><a href="https://stackoverflow.com/a/4841451/13903942">a += b not the same as a = a + b [duplicate]</a></li>
<li><a href="https://stackoverflow.com/questions/2347265/why-does-behave-unexpectedly-on-lists">Why does += behave unexpectedly on lists?</a></li>
</ul>
<h2>文件</h2>
<ul>
<li><a href="https://www.w3schools.com/python/gloss_python_assignment_operators.asp" rel="nofollow noreferrer">w3schools.com/python/gloss_python_assignment_operators.asp</a></li>
<li><a href="https://www.programiz.com/python-programming/operators" rel="nofollow noreferrer">programiz.com/python-programming/operators</a></li>
</ul>