Merge pull request #32 from nurdtechie98/master

Inbuilt functions . close #27

Author: inishchith

python/09-Inbuilt_functions.md

@@ -0,0 +1,154 @@
+<h1 align="center"><a href="#"> Strings </a></h1>
+
+* The Python interpreter has a number of functions and types built into it that are always available.
+* There is no need to import modules extra in order to use them.
+* A few functions that we will be covering here are-
+	* Map
+	* Filter
+	* Sort
+	* Max/Min
+	* Reduce
+
+## Map
+* It iterates through all the elements of a iterable and applies some specific funtion to each element of that iterable.
+* With multiple iterables, the iterator stops when the shortest iterable is exhausted
+
+### syntax
+```python
+r = map(func, seq)
+#takes each element in seq 
+#applies func function to them
+#inserts them to r
+
+```
+### implementation
+```python
+
+#for a single list involved
+a=['2011-12-22 46:31:11','2011-12-20 20:19:17', '2011-12-20 01:09:21']
+dt=list(map(str.split, a)) #split function is applied to each element and it returns a list corresponding to each element
+print(dt)
+
+#for multiple lists involved
+a = [1,2,3,4] 
+b = [17,12,11,10]
+print(list(map(lambda x,y:x+y, a,b)))
+#goes through each element of a,b 
+#adds them correspondingly till one of the lists end
+
+```
+Output
+```
+[['2011-12-22', '46:31:11'], ['2011-12-20', '20:19:17'], ['2011-12-20', '01:09:21']]
+[18, 14, 14, 14]
+```
+## Filter
+* As the name justifies,filter creates a list of elements for which a function returns true.
+
+### Syntax
+```python
+filter(filter_fnc,list)
+```
+### implementation
+```python
+def fn(x):
+	return (x<0) #(x<0) is condition automatically returns true or false
+number_list = range(-10, 10)
+less_than_zero = list(filter(fn, number_list))
+print(less_than_zero)
+```
+Output
+```
+[-10, -9, -8, -7, -6, -5, -4, -3, -2, -1]
+```
+
+## Sort/Sorted
+* Python lists have a built-in sort() method that modifies the list in-place and a sorted() built-in function that builds a new sorted list from an iterable
+* There are many ways to use them to sort data and there doesn't appear to be a single, central place in the various manuals describing them
+* The key difference between both is that sorted returns a new list whereas sort chsnges the original list itself.
+
+### syntax
+```python
+list.sort()
+sorted(container)#sort in ascending order
+sorted(list,reverse=True)#sort in descending order
+sorted(list,key=<insert the key>)#sort in ascending order of the key set
+```  
+### implementation
+```python
+
+a = [5, 2, 3, 1, 4]
+a.sort()# .sort() function is specific to lists
+print(a)
+
+chir={2: 'D', 1: 'B', 4: 'B', 3: 'E', 5: 'A'}# declaring a dictionary
+for ind in sorted(chir): #sorted is general approach, although return type is a list
+	print("{}:{}".format(ind,chir[ind]),end=" ")
+print()
+for ind in sorted(chir,reverse=True): #note the order is descending of the keys
+	print("{}:{}".format(ind,chir[ind]),end=" ")
+def gv(key):
+	return chir[key];
+print()
+for ind in sorted(chir,key=gv,reverse=True): #note the order is descending of the values of each key
+	print("{}:{}".format(ind,chir[ind]),end=" ")
+
+```
+Output
+```
+[1, 2, 3, 4, 5]
+1:B 2:D 3:E 4:B 5:A 
+5:A 4:B 3:E 2:D 1:B 
+3:E 2:D 1:B 4:B 5:A
+
+```
+## max/min
+* Return the greatets/smallest item in an iterable or the smallest of two or more arguments.
+* It can also be made to make use of key argument as used in sort function
+### implementation
+```python
+list = [1, 4, 3, 5,9,2]
+print(max(list)) #returns maximum value of list
+print(min(list)) #returns minimum value in the list
+print(max(list[2:-2])) #returns max value compined with slicing 
+print(min(list[4:])
+print(max(4,2,3,5))
+print(min(7,2,1,8,4))
+```
+Output
+```
+9
+1
+5
+9
+
+```
+
+## Reduce
+* Reduce is a really useful function for performing some computation on a list and returning the result.
+* It applies a rolling computation to sequential pairs of values in a list
+>note this not a inbuilt function as such because it needs to be imported from func tools but is pretty useful.
+
+### implementation
+```python
+#Normal way to find product of elements in a list
+product = 1
+list = [1, 2, 3, 4]
+for num in list:
+    product = product * num
+
+#Using reduce function to do so
+from functools import reduce
+def func(x,y):
+	return x*y
+product = reduce(func, [1, 2, 3, 4])
+
+```
+Output
+```
+24
+24
+```
+
+
+

python/10-user_defined_functions.md

@@ -8,7 +8,7 @@ After defining the function name and arguments(s) a block of program statement(s
 Here is the syntax of a user defined function.
 
 ## Syntax
-```
+```python
 def function_name(argument1, argument2, ...) :
     statement_1 
     statement_2
@@ -19,11 +19,11 @@ def function_name(argument1, argument2, ...) :
 Calling a function in Python is similar to other programming languages, using the function name, parenthesis (opening and closing) and parameter(s). See the syntax, followed by an example.
 
 ### Syntax
-```
+```python
 function_name(arg1, arg2)
 ```
 ### Example :
-```
+```python
 def avg_number(x, y):  
     print("Average of ",x," and ",y, " is ",(x+y)/2)  
 avg_number(3, 4)  
@@ -42,15 +42,15 @@ Average of 3 and 4 is 3.5
 ## Function without arguments :
 
 The following function has no arguments.
-```
+```python
 def function_name() :
     statement_1 
     statement_2
     ....
 ```
 ### Example :
 
-```
+```python
 def printt():  
     print("I Love CodeCell")  
     print("I Love CodeCell")  
@@ -73,7 +73,7 @@ I Love CodeCell
 ## The Return statement in function
 
 In Python the return statement (the word return followed by an expression.) is used to return a value from a function, return statement without an expression argument returns none. See the syntax.
-```
+```python
 def function_name(argument1, argument2, ...) :
     statement_1 
     statement_2
@@ -85,7 +85,7 @@ function_name(arg1, arg2)
 ### Example :
 
 The following function returns the square of the sum of two numbers.
-```
+```python
 def nsquare(x, y):  
     return (x*x + 2*x*y + y*y)  
 print("The square of the sum of 2 and 3 is : ", nsquare(2, 3))  

python/readme.md

@@ -11,7 +11,7 @@
  6. [Arrays/Lists](./06-Lists.md)
  7. [Dictionaries](./07-Dictionaries.md)
  8. [Sets](./08-Sets.md)
- 9. [In build functions]()
+ 9. [In build functions](./09-Inbuilt_functions.md)
  10. [User defined functions](./10-user_defined_functions.md)
  11. [Lambda](./11-Lambda.md)
  12. [Modules](./12-Modules.md)