#loops
programming·@programmingtech·
0.000 HBD#loops
<html> <pre><code>for and while loops </code></pre> <h2>"For" Loop</h2> <p>For loops iterate over a given sequence. Here is an example:</p> <p><code>primes = [2, 3, 5, 7]</code><br> <code>for prime in primes:</code><br> <code> print prime</code></p> <p>Copy<em>Note: Copy and Paste Code into Compiler</em><br> <a href="https://steemit.com/compiler/index1.html"><strong> </strong></a><br> </p> <p>For loops can iterate over a sequence of numbers using the "range" and "xrange" functions. The difference between range and xrange is that the range function returns a new list with numbers of that specified range, whereas xrange returns an iterator, which is more efficient. (Python 3 uses the range function, which acts like xrange). Note that the xrange function is zero based.</p> <p><code>for x in xrange(5): # or range(5)</code><br> <code> print x</code><br> <code># Prints out 3,4,5</code><br> <code>for x in xrange(3, 6): # or range(3, 6)</code><br> <code> print x</code><br> <code># Prints out 3,5,7</code><br> <code>for x in xrange(3, 8, 2): # or range(3, 8, 2)</code><br> <code> print x</code></p> <p>Copy<em>Note: Copy and Paste Code into Compiler</em><br> </p> <h2>"While" Loops</h2> <p>While loops repeat as long as a certain boolean condition is met. <br> For example:</p> <p><code>count = 0</code><br> <code>while count < 5:</code><br> <code> print count</code><br> <code> count += 1 # This is the same as count = count + 1</code></p> <p>Copy<em>Note: Copy and Paste Code into Compiler</em><br> <a href="https://steemit.com/compiler/index1.html"><strong> </strong></a></p> <h2>"Break" and "Continue"</h2> <p>Break is used to exit a for loop or a while loop, whereas continue is used to skip the current block, and return to the "for" or "while" statement. A few examples:</p> <p><code>count = 0</code><br> <code>while True:</code><br> <code> print count</code><br> <code> count += 1</code><br> <code> if count >= 5:</code><br> <code> break</code><br> </p> <p><code># Prints out only odd numbers - 1,3,5,7,9</code><br> <code>for x in xrange(10):</code><br> <code> # Check if x is even</code><br> <code> if x % 2 == 0:</code><br> <code> continue</code><br> <code> print x</code></p> <p>Copy<em>Note: Copy and Paste Code into Compiler</em><br> <a href="https://steemit.com/compiler/index1.html"><strong> </strong></a></p> <h2>Can we use "else" clause for loops?</h2> <p>unlike languages like C,C++. we can use else for loops. When the loop condition of "for" or "while" statement fails then code part in "else" is executed. If break statement is executed inside for loop then the "else" part is skipped. Note that "else" part is executed even if there is a continue statement. <br> Here are a few examples:<code>count=0</code><br> <code>while(count<5):</code><br> <code> print count</code><br> <code> count +=1</code><br> <code>else:</code><br> <code> print "count value reached %d" %(count)</code><br> </p> <p><code># Prints out 1,2,3,4</code><br> <code>for i in xrange(1,10):</code><br> <code> if(i%5==0):</code><br> <code> break</code><br> <code> print i</code><br> <code>else:</code><br> <code> print "this is not printed because for loop is terminated because of break but not due to fail in condition"</code></p> </html>