Article: Data-Structure-ARRAYS.md

Data-Structure-Arrays.md

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+# Data Structure Arrays
+
+Internally, `array` is a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An `array` is used to store a collection of data, but it is often more useful to think of an `array` as a collection of variables of the same type.
+
+`array` consists of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.
+
+## Arrays in Python
+
+Python doesn't have a native `array` data structure. An `array` in Python should not be confused with `list`. The major difference between a `list`
+and an `array` in Python is that a `list` can have different types of values whereas an `array` should have all the values of same type.
+
+#### Declaration of `array`
+
+```python
+from array import array
+intarray = array('i') # Declares an array of integer type
+```
+
+#### Adding elements to `array`:
+
+```python
+intarray.append(1) # Adds an integer value of 1 to the array
+intarray.append(0) # Adds an integer value of 0 to the array
+intarray.append(-1) # Adds an integer value of -1 to the array
+intarray.append(1) # Again adds an integer value of 1 to the array
+
+intarray.append('d') # Would give a TypeError as the array is of integer type. 
+
+#Resolve the above error and then move ahead.
+```
+
+#### Printing an `array`: 
+
+```python
+print(intarray) # Returns array('i', [1, 4, -1])
+print(intarray[0]) # Returns 1 which is the element at index 0 of the array
+print(intarray[3]) # Would give IndexError as there is no element at index 3 of array. 
+
+#Resolve the above error and then move ahead.
+
+# To print all the elements of the array
+for i in intarray:
+	print(i)
+```
+
+#### Basic operations on `array`: 
+
+```python
+len(intarray) # Returns the length of the array i.e. 3
+intarray.itemsize # Returns length in bytes of one array item i.e. 4 as it is an integer
+intarray.count(1) # Returns the number of occurrences of 1 in the array i.e. 2
+intarray.insert(1, 3) # Insert a new item with value x in the array before position i
+intarray.remove(1) # Remove the first occurrence of 1 from the array
+intarray.reverse() # Reverse the order of the items in the array
+intarray.pop(1) # Removes the item with the index 1 from the array and returns it 
+```
+
+:rocket: [Run Code](https://repl.it/CWJB)
+
+[Official Docs](https://docs.python.org/3.5/library/array.html)