What does <function at ...> mean
<p>Here's the code:</p>

<pre><code>def my_func(f, arg):
  return f(arg)

print((lambda x: 2*x*x, (5)))

&gt;&gt;&gt;(&lt;function &lt;lambda&gt; at 0x10207b9d8&gt;, 5)
</code></pre>

<p>How to solve the error, and can some please explain in a clear language what exactly that error means.</p>

<p>There is no error; you simply supplied two arguments to <code>print</code>, the <code>lambda x: 2*x*x</code> and <code>5</code>. You're not calling your anonymous function rather, just passing it to <code>print</code>.</p>

<p><code>print</code> will then call the objects <code>__str__</code> method which returns what you see:</p>

<pre><code>&gt;&gt;&gt; str(lambda x: 2*x*x)  # similarly for '5'
'&lt;function &lt;lambda&gt; at 0x7fd4ec5f0048&gt;'
</code></pre>

<p>Instead, fix your parenthesis to actually <em>call</em> the lambda with the <code>5</code> passed as the value for <code>x</code>:</p>

<pre><code>print((lambda x: 2*x*x)(5))
</code></pre>

<p>which prints out <code>50</code>.</p>

<hr>

<blockquote>
  <p>What's the general meaning of <code>&lt;function at 0x ...&gt;</code>?</p>
</blockquote>

<p>That's simply the way Python has chosen to represent function objects when printed. Their <code>str</code> takes the name of the function and the <code>hex</code> of the <code>id</code> of the function and prints it out. E.g:</p>

<pre><code>def foo(): pass
print(foo) # &lt;function foo at 0x7fd4ec5dfe18&gt;
</code></pre>

<p>Is created by returning the string:</p>

<pre><code>"&lt;function {0} at {1}&gt;".format(foo.__name__, hex(id(foo)))
</code></pre>

python function python-3.x