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    <p>In my opinion you have two options:</p> <ul> <li><p>Just try to convert it to an <code>int</code>, but catch the exception:</p> <pre><code>try: value = int(value) except ValueError: pass # it was a string, not an int. </code></pre> <p>This is the Ask Forgiveness approach.</p></li> <li><p>Explicitly test if there are only digits in the string:</p> <pre><code>value.isdigit() </code></pre> <p><a href="http://docs.python.org/2/library/stdtypes.html#str.isdigit"><code>str.isdigit()</code></a> returns <code>True</code> only if all characters in the string are digits (<code>0</code>-<code>9</code>).</p> <p>The <code>unicode</code> / Python 3 <code>str</code> type equivalent is <a href="https://docs.python.org/2/library/stdtypes.html#unicode.isdecimal"><code>unicode.isdecimal()</code></a> / <a href="https://docs.python.org/3/library/stdtypes.html#str.isdecimal"><code>str.isdecimal()</code></a>; only Unicode decimals can be converted to integers, as not all digits have an actual integer value (<a href="http://codepoints.net/U+00B2">U+00B2 SUPERSCRIPT 2</a> is a digit, but not a decimal, for example).</p> <p>This is often called the Ask Permission approach, or Look Before You Leap. </p></li> </ul> <p>The latter will not detect all valid <code>int()</code> values, as whitespace and <code>+</code> and <code>-</code> are also allowed in <code>int()</code> values. The first form will happily accept <code>' +10 '</code> as a number, the latter won't.</p> <p>If your expect that the user <em>normally</em> will input an integer, use the first form. It is easier (and faster) to ask for forgiveness rather than for permission in that case.</p>
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    1. POHow to check if a variable is an integer or a string?
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    1. USMartijn Pieters
    1. USMartijn Pieters
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    1. POHow to check if a variable is an integer or a string?
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    1. COThe are other options. Better say that those two options are just what you would recommend yourself.
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      1. USAlexei Sholik
    2. CO@android: The other options are overkill for most situations. Yet, quantified it.
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      1. USMartijn Pieters
    3. COThe problem is that I don't really understand try...except, so if you could explain it more thoroughly, that would be great.
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      1. USuser2154354
 

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