Why is there no goto in Python?

Yes, there is no goto statement in Python. Let us first understand what is a goto in C Language. However, the usage of goto is also discouraged in C.

The goto statement in C programming provides an unconditional jump from the 'goto' to a labelled statement in the same function. Following is the syntax ?

goto label;
..
.
label: statement;

Example

Let us now see a C program for goto ?

#include <stdio.h>
int main () {
   int a = 10;
   LOOP:do {
      if( a == 15) {
         /* skip the iteration */
         a = a + 1;
         goto LOOP;
      }
      printf("a = %d\n", a);
      a++;
   }while( a < 20 );
   return 0;
}

Output

a = 10
a = 11
a = 12
a = 13
a = 14
a = 16
a = 17
a = 18
a = 19

NOTE ? The use of goto statement is highly discouraged in C language as well.

No GoTo in Python

In Python, there?s no need of goto since we can accomplish the same with if statements and or, and, and if-else expressions & loop with while and for statements, containing continue and break.

User-defined Exceptions

Use user-defined exceptions as an alternative ?

class goto1(Exception):
   pass
class goto2(Exception):
   pass
class goto3(Exception):
   pass

def loop():
   print('start')
   num = input()
   try:
      if num<=0:
         raise goto1
      elif num<=2:
         raise goto2
      elif num<=4:
         raise goto3
      elif num<=6:
         raise goto1
      else:
         print('end')
         return 0
   except goto1 as e:
      print('goto1')
      loop()
   except goto2 as e:
      print('goto2')
      loop()
   except goto3 as e:
      print('goto3')
      loop()

Nested Methods

Example

Use nested methods as another alternative ?

def demo():
   print("In the demo() function")
def inline():
   print("In")
inline()
demo()

Output

In
In the demo() function

The goto-statement module

It is a function decorator to use goto in Python. Tested on Python 2.6 through 3.6 and PyPy. Install it using the pip ?

Note: Works till Python 3.6

pip install goto-statement

Let us see an example ?

# Python 3.6
from goto import with_goto

@with_goto
def range(start, stop):
   i = start
   result = []

   label .begin
   if i == stop:
      goto .end

   result.append(i)
   i += 1
   goto .begin

   label .end
   return result