added Ex 27

ex_27.py

@@ -0,0 +1,33 @@
+from defusedxml import ElementTree
+from collections import deque
+import matplotlib.pyplot as plt
+
+data = {"Germany": deque()
+	, "France": deque()
+	, "Italy": deque()
+	, "United States": deque()
+}
+
+with open("data/API_NY.GDP.MKTP.KN_DS2_en_xml_v2_10230884.xml") as fin:
+	tree = ElementTree.parse(fin)
+	for record in tree.getroot().find("data").findall("record"):
+		this_data = {field.get("name"): field.text for field in record.findall("field")}
+		if(this_data["Country or Area"] in data):
+			if(this_data["Value"] != None):
+				data[this_data["Country or Area"]].append((this_data["Year"], this_data["Value"]))
+
+			
+
+class Data(object):
+	def __init__(self, raw_data):
+		self.x = [int(k) for k, v in raw_data]
+		self.y = [float(v) for k, v in raw_data]
+
+data = {k: Data(v) for k,v in data.items()}
+
+plots = [plt.plot(v.x, v.y, label=k)[0] for k, v in data.items()]
+
+plt.legend(handles = plots)
+
+plt.show()
+