Short-circuit evaluation like Python's "and" while storing results of checks
<p>I have multiple expensive functions that return results.  I want to return a tuple of the results of all the checks if all the checks succeed.  However, if one check fails I don't want to call the later checks, like the short-circuiting behavior of <code>and</code>.  I could nest <code>if</code> statements, but that will get out of hand if there are a lot of checks.  How can I get the short-circuit behavior of <code>and</code> while also storing the results for later use?</p>

<pre><code>def check_a():
    # do something and return the result,
    # for simplicity, just make it "A"
    return "A"

def check_b():
    # do something and return the result,
    # for simplicity, just make it "B"
    return "B"

...
</code></pre>

<p>This doesn't short-circuit:</p>

<pre><code>a = check_a()
b = check_b()
c = check_c()

if a and b and c:
    return a, b, c
</code></pre>

<p>This is messy if there are many checks:</p>

<pre><code>if a:
   b = check_b()

   if b:
      c = check_c()

      if c:
          return a, b, c
</code></pre>

<p>Is there a shorter way to do this?</p>

<p>If the main objection is</p>

<blockquote>
  <p>This is messy if there are many checks:</p>
</blockquote>

<pre><code>if a:
   b = check_b()

   if b:
      c = check_c()

      if c:
          return a, b, c
</code></pre>

<p>A fairly nice pattern is to reverse the condition and return early</p>

<pre><code>if not a:
    return  # None, or some value, or however you want to handle this
b = check_b()
if not b:
    return
c = check_c()
if not c:
    return

# ok, they were all truthy
return a, b, c
</code></pre>

python short-circuiting