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    <p>Dead simple, just nest your functions:</p> <pre><code>def make_multiplier(x): def multiplier(y): return x * y return multiplier </code></pre> <p>Nested functions automatically look up unknown variables (<code>x</code> in this case) from their surrounding scope, using the value of <code>x</code> as it was when the outer function was called. The thing to remember here is that functions are just objects too, you can store them in a variable just like you can with other python objects, and defer calling them.</p> <p>This gives:</p> <pre><code>&gt;&gt;&gt; def make_multiplier(x): ... def multiplier(y): ... return x * y ... return multiplier ... &gt;&gt;&gt; f = make_multiplier(10) &gt;&gt;&gt; f(1) 10 &gt;&gt;&gt; f(2) 20 &gt;&gt;&gt; g = make_multiplier(5) &gt;&gt;&gt; g(1) 5 &gt;&gt;&gt; f(3) 30 </code></pre> <p>Note how <code>g</code> was given a different value for <code>x</code>, which is independent from the value for <code>x</code> in <code>f</code>.</p> <p>You could use a lambda as well; lambdas are just anonymous functions limited to one expression; that's enough here:</p> <pre><code>def make_multiplier(x): return lambda y: x * y </code></pre> <p>Another alternative technique is binding <code>x</code> to a keyword parameter, which means you could override it if you so wish:</p> <pre><code>def make_multiplier(x): def multiply(y, x=x): return x * y return multiply </code></pre> <p>or the lambda version:</p> <pre><code>def make_multiplier(x): return lambda y, x=x: x * y </code></pre> <p>and then pass in one or two arguments to the returned callable:</p> <pre><code>&gt;&gt;&gt; f = make_multiplier(10) &gt;&gt;&gt; f(5) 50 &gt;&gt;&gt; f(5, 3) 15 </code></pre>
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    1. POHow to write a function that returns a function in Python?
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    1. USMartijn Pieters
    1. USMartijn Pieters
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    1. COHint != giving away the answer.
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      1. USMatt Ball
    2. COYou can also use the `lambda` syntax to simplify this case.
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      1. USWill
    3. CO@Will: `lambda` is just semantics, and then you have to explain the difference too. Nesting a function is simpler.
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