From a3d3368d9f024052632dc87b5d52e26a223c7869 Mon Sep 17 00:00:00 2001
From: Kyle K <kylek389@gmail.com>
Date: Sat, 1 Apr 2017 03:34:41 -0500
Subject: interator / generators exmaples

---
 .gitignore    |  1 +
 generators.py | 34 ++++++++++++++++++++++++++++++++++
 iterator.py   | 26 ++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 generators.py
 create mode 100644 iterator.py

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9f11b75
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea/
diff --git a/generators.py b/generators.py
new file mode 100644
index 0000000..cdc0597
--- /dev/null
+++ b/generators.py
@@ -0,0 +1,34 @@
+
+# here is a simple generator
+# a 'yield' returns an expression which then gets invoked in for loop, a num by itself is an expression
+def gen1():
+    yield 1
+    yield 2
+    yield 3  # at this point python's list implemention will raise StopIteration since were at last yield
+
+a = [i for i in gen1()]
+print(a)
+
+
+# following example depicts how Comprehensions are syntactically almost the same except the use of () instead of []
+
+gen2 = ("{0} is even".format(i) for i in range(0, 10) if i % 2 == 0)
+print(gen2.__next__())  # get a value
+print(list(gen2))  # loop till the end
+#print(gen2.__next__())  # this would error, generator can only be looped once
+
+# output
+#
+# 0 is even
+# ['2 is even', '4 is even', '6 is even', '8 is even']
+
+
+
+# here is a Generator version of string reversal from interator.py
+
+def reverseString2(data):
+    for index in range(len(data) - 1, -1, -1):
+        yield data[index]
+
+for c in reverseString2('barfoo'):
+    print(c)
diff --git a/iterator.py b/iterator.py
new file mode 100644
index 0000000..2b1e14e
--- /dev/null
+++ b/iterator.py
@@ -0,0 +1,26 @@
+# this class implements an iterator
+# python needs to be told when to stop iterating, this is done by raising StopIteration exception
+
+class ReverseString():
+    def __init__(self, data):
+        self.data = data
+        self.index = len(data)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self.index == 0:
+            raise StopIteration
+        self.index -= 1
+        return self.data[self.index]
+
+
+def main():
+    foo = ReverseString('foobar')
+    for c in foo:
+        print(c)
+
+
+if __name__ == "__main__":
+    main()
-- 
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