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Boston Python Workshop 4/Friday/Tutorial: Difference between revisions
Boston Python Workshop 4/Friday/Tutorial (view source)
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, 12 years ago→compound conditionals: and and or
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<pre>
if
print "
</pre>
That was our first multi-line piece of code, and the way to enter it at a Python prompt is a little different. First, type the <code>if
Type 4 spaces, and then type <code>print "
<pre>
>>> if
... print "
...
Six is greater than five!
</pre>
So what is going on here? When Python encounters the <code>if</code> keyword, it <i>evaluates</i> the <i>expression</i> following the keyword and before the colon. If that expression is <b>True</b>, Python executes the code in the indented code block under the <code>if</code> line. If that expression is <b>False</b>, Python skips over the code block.
In this case, because
<pre>
if
print "
</pre>
<pre>
if "banana" in "bananarama":
print "
</pre>
====more choices: <code>if</code> and <code>else</code>====
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====compound conditionals: <code>and</code> and <code>or</code>====
You can check multiple expressions together using the <code>and</code> and <code>or</code> keywords. If two expressions are joined by an <code>and</code>, they <b>both</b> have to be True for the overall expression to be True. If two expressions are joined by an <code>or</code>, as long as <b>at least one</b> is True, the overall expression is True.
Try typing these out and see what you get:
<pre>
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<pre>
"a" in "hello" or "e" in "hello"
</pre>
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If color had been "purple", that code wouldn't have printed anything.
<b>Remember! = is for assignment, == is for comparison.</b>
==Writing Functions==
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