diff --git a/add.py b/add.py
new file mode 100644
index 0000000..c744d31
--- /dev/null
+++ b/add.py
@@ -0,0 +1,4 @@
+def add(a, b):
+  print a + b
+  
+add(1, -2)
\ No newline at end of file
diff --git a/dict.py b/dict.py
new file mode 100644
index 0000000..6a5f147
--- /dev/null
+++ b/dict.py
@@ -0,0 +1,20 @@
+D = {}
+
+def makeD(s):
+  a = s.split(";")
+  for i in a:
+    key, val = i.split("=")
+    D[key] = val
+
+def makeDshort(s):
+    return dict([i.split("=") for i in s.split(";")])
+  
+def dictocs(d):
+  s = ''
+  for i in d:
+    s += str(i) + '=' + str(d[i])
+  return s
+
+makeD("a=bc;d=efg;h=ijkl;m=n")
+print D
+print dictocs({'a': 'bc', 'h': 'ijkl', 'm': 'n', 'd': 'efg'})
\ No newline at end of file
diff --git a/files.py b/files.py
new file mode 100644
index 0000000..4cd03f9
--- /dev/null
+++ b/files.py
@@ -0,0 +1,7 @@
+try:
+	with open('first.txt', 'r') as inp:
+		with open('second.txt', 'w') as out:
+			for line in inp:
+				out.write(line)
+except IOError:
+        print "Wrong file or file path"
diff --git a/inherit dict.py b/inherit dict.py
new file mode 100644
index 0000000..d6c84b1
--- /dev/null
+++ b/inherit dict.py	
@@ -0,0 +1,60 @@
+
+class ITEMNOTINMENU(Exception):
+  pass
+class WrongPrice(Exception):
+  pass
+
+class Menu(dict):
+  def __getitem__(self, i):
+    if self.get(i) is None:
+      raise ITEMNOTINMENU
+    else:
+      return self.get(i)
+    
+class Order(dict):
+  def __init__(self, m):
+    self.d = m
+    dict.__init__(self)
+      
+  def __setitem__(self, key, item): 
+    if key in self.d:
+      if self.d[key] == item:
+        self.update({key : item})
+      else:
+        raise WrongPrice
+    else:
+      raise ITEMNOTINMENU
+      
+  def show(self):
+    print 'order :'
+    for i in self.items():
+      print '\t' + str(i[0]) + ' costs ' + str(i[1])
+    
+  
+c = Menu()
+c['vada'] = 10
+c['idly'] = 30
+print c['vada']
+try:
+  print c['unknown']
+except ITEMNOTINMENU:
+  print 'not in menu'
+  
+o1 = Order(c)
+o2 = Order(c)
+try:
+  o1['vada'] = 10
+except ITEMNOTINMENU:
+  print 'not in menu'
+except WrongPrice:
+  print 'wrong price'
+
+try:
+  o2['idly'] = 30
+except ITEMNOTINMENU:
+  print 'not in menu'
+except WrongPrice:
+  print 'wrong price'
+ 
+o1.show()
+o2.show()
diff --git a/menu.py b/menu.py
new file mode 100644
index 0000000..eebbdac
--- /dev/null
+++ b/menu.py
@@ -0,0 +1,12 @@
+class Menu:
+  def __init__(self):
+    self.d = {'vada' : 10}
+  def show(self):
+    for i in self.d.items():
+      print str(i[0]) + ' costs ' + str(i[1])
+  def add(self, a, b):
+    self.d[a] = b
+  
+c = Menu()
+c.add('idly', 20)
+c.show()
\ No newline at end of file
diff --git a/order.py b/order.py
new file mode 100644
index 0000000..966151c
--- /dev/null
+++ b/order.py
@@ -0,0 +1,76 @@
+class ITEMNOTINMENU(Exception):
+  pass
+class WrongPrice(Exception):
+  pass
+
+class Menu:
+  def __init__(self):
+    self.d = {'vada' : 10, 'idly' : 20}
+    
+  def __contains__(self, key):
+    return key in self.d
+    
+  def __getitem__(self, i):
+    if i in self.d:
+      return self.d[i]
+    else:
+      raise ITEMNOTINMENU
+      
+  def __setitem__(self, key, item): 
+    self.d[key] = item
+    
+  def show(self):
+    print 'menu :'
+    for i in self.d.items():
+      print '\t' + str(i[0]) + ' costs ' + str(i[1])
+      
+  def add(self, a, b):
+    self.d[a] = b
+    
+class Order():
+  d = Menu()
+  def __init__(self, m):
+    self.d = m
+    self.ord = {}
+      
+  def __getitem__(self, i):
+    if i in self.ord:
+      return self.ord[i]
+    else:
+      raise ITEMNOTINMENU
+      
+  def __setitem__(self, key, item): 
+      if key in self.d:
+        if self.d[key] == item:
+          self.ord[key] = item
+        else:
+          raise WrongPrice
+      else:
+        raise ITEMNOTINMENU
+      
+  def show(self):
+    print 'order :'
+    for i in self.ord.items():
+      print '\t' + str(i[0]) + ' costs ' + str(i[1])
+    
+  
+c = Menu()
+c['idly'] = 20
+try:
+  print c['unknown']
+except ITEMNOTINMENU:
+  print 'not in menu'
+  
+c.show()
+o1 = Order(c)
+o2 = Order(c)
+try:
+  o1['vada'] = 10
+  o2['idly'] = 20
+except ITEMNOTINMENU:
+  print 'not in menu'
+except WrongPrice:
+  print 'wrong price'
+  
+o1.show()
+o2.show()
diff --git a/orderInheritance.py b/orderInheritance.py
new file mode 100644
index 0000000..81ec9eb
--- /dev/null
+++ b/orderInheritance.py
@@ -0,0 +1,78 @@
+class ITEMNOTINMENU(Exception):
+  pass
+class WrongPrice(Exception):
+  pass
+
+class Help(object):
+  def getitem(self, i, a):
+    if i in a:
+      return a[i]
+    else:
+      raise ITEMNOTINMENU
+      
+  def show(self, a):
+    for i in a.items():
+      print '\t' + str(i[0]) + ' costs ' + str(i[1])
+
+class Menu(Help):
+  def __init__(self):
+    self.d = {'vada' : 10, 'idly' : 20}
+    
+  def __getitem__(self, i):
+    return super(Menu, self).getitem(i, self.d)
+  
+  def __contains__(self, key):
+    return key in self.d
+      
+  def __setitem__(self, key, item): 
+    self.d[key] = item
+    
+  def show(self):
+    print 'menu :'
+    super(Menu, self).show(self.d)
+      
+  def add(self, a, b):
+    self.d[a] = b
+    
+class Order(Help):
+  def __init__(self, m):
+    self.d = m
+    self.ordL = {}
+      
+  def __getitem__(self, i):
+    return super(Order, self).getitem(i, self.ordL)
+      
+  def __setitem__(self, key, item): 
+    if key in self.d:
+      if self.d[key] == item:
+        self.ordL[key] = item
+      else:
+        raise WrongPrice
+    else:
+      raise ITEMNOTINMENU
+      
+  def show(self):
+    print 'order :'
+    super(Order, self).show(self.ordL)
+    
+  
+c = Menu()
+c['idly'] = 20
+try:
+  print c['unknown']
+except ITEMNOTINMENU:
+  print 'not in menu'
+  
+c.show()
+o1 = Order(c)
+o2 = Order(c)
+try:
+  o1['vada'] = 10
+  o2['idly'] = 20
+except ITEMNOTINMENU:
+  print 'not in menu'
+except WrongPrice:
+  print 'wrong price'
+  
+o1.show()
+o2.show()
\ No newline at end of file
diff --git a/root.py b/root.py
new file mode 100644
index 0000000..ec6c878
--- /dev/null
+++ b/root.py
@@ -0,0 +1,10 @@
+def root(a, b, c):
+  sq = b * b - 4 * a * c
+  if sq < 0:
+    r1 = str(pow(abs(b * b - 4 * a * c), 0.5)) + 'i'
+    r2 = -b / 2 * a
+    return str(r2) + ' + ' + r1, str(r2) + ' - ' + r1
+  else:
+	  return (-b + pow(b * b - 4 * a * c, 0.5)) / (2 * a), (-b - pow(b * b - 4 * a * c, 0.5)) / (2 * a)
+
+print root(2, 3, 5)
\ No newline at end of file
diff --git a/rootV2.py b/rootV2.py
new file mode 100644
index 0000000..a43de1e
--- /dev/null
+++ b/rootV2.py
@@ -0,0 +1,6 @@
+import cmath
+
+def root(a, b, c):
+	  return (-b + cmath.sqrt(b * b - 4 * a * c)) / (2 * a), (-b - cmath.sqrt(b * b - 4 * a * c)) / (2 * a)
+
+print root(2, 3, 5)