iterators and generators chapter

--HG--
rename : humansize.py => examples/humansize.py
rename : roman1.py => examples/roman1.py
rename : roman2.py => examples/roman2.py
rename : roman3.py => examples/roman3.py
rename : roman4.py => examples/roman4.py
rename : roman5.py => examples/roman5.py
rename : roman6.py => examples/roman6.py
rename : roman7.py => examples/roman7.py
rename : roman8.py => examples/roman8.py
rename : romantest1.py => examples/romantest1.py
rename : romantest2.py => examples/romantest2.py
rename : romantest3.py => examples/romantest3.py
rename : romantest4.py => examples/romantest4.py
rename : romantest5.py => examples/romantest5.py
rename : romantest6.py => examples/romantest6.py
rename : romantest7.py => examples/romantest7.py
rename : romantest8.py => examples/romantest8.py

examples/humansize.py

@@ -0,0 +1,65 @@
+"""Convert file sizes to human-readable form.
+
+Available functions:
+approximate_size(size, a_kilobyte_is_1024_bytes)
+    takes a file size and returns a human-readable string
+
+Examples:
+>>> approximate_size(1024)
+'1.0 KiB'
+>>> approximate_size(1000, False)
+'1.0 KB'
+
+"""
+
+SUFFIXES = {1000: ['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'],
+            1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']}
+
+def approximate_size(size, a_kilobyte_is_1024_bytes=True):
+    """Convert a file size to human-readable form.
+
+    Keyword arguments:
+    size -- file size in bytes
+    a_kilobyte_is_1024_bytes -- if True (default), use multiples of 1024
+                                if False, use multiples of 1000
+
+    Returns: string
+
+    """
+    if size < 0:
+        raise ValueError('number must be non-negative')
+
+    multiple = 1024 if a_kilobyte_is_1024_bytes else 1000
+    for suffix in SUFFIXES[multiple]:
+        size /= multiple
+        if size < multiple:
+            return "{0:.1f} {1}".format(size, suffix)
+
+    raise ValueError('number too large')
+
+if __name__ == "__main__":
+    print(approximate_size(1000000000000, False))
+    print(approximate_size(1000000000000))
+
+# Copyright (c) 2009, Mark Pilgrim, All rights reserved.
+# 
+# Redistribution and use in source and binary forms, with or without modification,
+# are permitted provided that the following conditions are met:
+# 
+# * Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+# 
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.