Create basic_commands.py

Author: ujjwalkarn

Diff for: basic_commands.py

@@ -0,0 +1,80 @@
+>>> a = ['a', 'b', 'c', 'd', 'e']
+>>> for index, item in enumerate(a): print index, item
+...
+0 a
+1 b
+2 c
+3 d
+4 e
+
+
+
+
+#convert a list to string:
+
+list1 = ['1', '2', '3']
+str1 = ''.join(list1)
+
+Or if the list is of integers, convert the elements before joining them.
+
+list1 = [1, 2, 3]
+str1 = ''.join(str(e) for e in list1)
+
+
+
+#FIND method
+
+str.find(str2, beg=0 end=len(string))
+
+Parameters
+str2 -- This specifies the string to be searched.
+beg -- This is the starting index, by default its 0.
+end -- This is the ending index, by default its equal to the lenght of the string.
+
+Return Value
+This method returns index if found and -1 otherwise.
+
+str1 = "this is string example....wow!!!";
+str2 = "exam";
+
+print str1.find(str2);
+print str1.find(str2, 10);
+print str1.find(str2, 40);
+
+#15
+#15
+#-1
+
+
+
+
+
+#2D LIST PYTHON
+
+# Creates a list containing 5 lists initialized to 0
+Matrix = [[0 for x in range(5)] for x in range(5)] 
+You can now add items to the list:
+
+Matrix[0][0] = 1
+Matrix[4][0] = 5
+
+print Matrix[0][0] # prints 1
+print Matrix[4][0] # prints 5
+
+
+if you have a simple two-dimensional list like this:
+
+A = [[1,2,3,4],
+     [5,6,7,8]]
+then you can extract a column like this:
+
+def column(matrix, i):
+    return [row[i] for row in matrix]
+Extracting the second column (index 1):
+
+>>> column(A, 1)
+[2, 6]
+Or alternatively, simply:
+
+>>> [row[1] for row in A]
+[2, 6]