Python Goto Statement

We all know that Python is the most basic and widely used programming language in the world. It is also one of the world's most popular and widely used languages. Everyone, whether a beginner or an expert, uses Python, and one of the most overlooked statements in Python is the goto statement. In this tutorial, we'll look at what the goto statement is and how to use it in Python in a subtle way.

A goto statement is so named because this piece of code unconditionally jumps your code through the goto statement to a stated statement that is marked with the goto statement. In layman's terms, it is commonly used whenever a programmer wishes to skip a specific number of functions or statements.

Even though programmers prefer the go to statement, the go to statement falls short when it comes to auditing. It should be noted that it becomes difficult for programmers to change any programme content, and locating the precise destination of the goto statement is time-consuming. It is because of this that the code execution conveniently jumps from one function to another.

The syntax of the go to statement is as follows:

# go to in python

goto label;

....

....

Label:

Label:

....

....

goto label;

### Note : The label is just a sample word and it should be replaced the appropriate text or statement.

# For example: goto return;

The goto statements’ iterations

The comefrom statement is another statement that works in the same way as goto. The comefrom statement, on the other hand, has the inverse meaning of the goto statement. In reality, both goto and comefrom statements give a Python programme a lot of flexibility and scalability. This enables a programme to control the programme flow mechanism. It also has the ability to control the flow of idioms.

One thing to keep in mind is that, as with any Python programme, we must first import the goto and comefrom statements from the main library. As an example:

# importing goto and comefrom in the main library

from goto import goto, comefrom, label

When one uses go to in Python, one is essentially asking the interpreter to execute another line of statements instead of the current one. In the "label" section, you must specify the target statement that you want the interpreter to execute at that time. Label.thelabel as an example

The command is coming from somewhere, according to a comefrom statement. That is, it instantiates the command to come from another instance rather than going to a different line of code.

The syntax of the comefrom statement is as follows:

Label .somewhere

comefrom .somewhere

Come from is a very critical factor and is used as a debugging aid during programming.

Computed goto

The computed goto statement is a common variation of the goto statement in Python. In this case, all that is required is to define the Python index at the start of the code and then refer to it with a hashtag.

Let’s inspect an example for this :

i = calculateLabelName()

Goto *i

Restrictions within the goto statement:

Python, like other lines of code and coding platforms, has a number of restrictions on the comefrom and goto statements. Here are the restrictions:

• Programmers cannot use both statements to jump between modules or functions at the same time.
• It is not always possible to jump to the ultimate clause or the centre of any loop.
• Because the exception line cannot be found in the first place, neither of these statements will be useful.

Let us look at some examples to understand better:

Example: Implementation of goto statement

from goto import goto, label

    for x in range(1, 10):

    for y in range(1, 20):

    for z in range(1, 30):

    print x,y,z

    if z == 3:

       goto .end

       label .end

   print "Finished"

The above example is used to break free from any loop that may be nested however deeply.

Example: Cleaning after task failure

# Take these as real-worker functions.

from goto import goto, label

   def settingUp():

       print "settingUp"

   def doPrimaryTask():

        print 0;

        return True

   def doSecondaryTask():

        print 1;

        return True

   def doThirdTask():

        print 2;

        return False # It pretends to fail.

   def doFourthTask():

        print 3;

        return True

   def cleanUp():

        print "cleanUp"

#  This function allows the third task to cleanup

def bigFunction3():

    settingUp()

    if not doPrimaryTask():

       goto .cleanup

    if not doSecondaryTask():

       goto .cleanup

    if not doThirdTask():

       goto .cleanup

    if not doFourthTask():

       goto .cleanup

    label .cleanup

    cleanUp()

bigFunction3()

print "bigFunction3 done"

Thus, the goto statement in Python is a very useful command that is used for both auditing and debugging purposes. Although they are underutilized in daily programming, using a go to statement frequently yields very impressive results.

Example: Miscellaneous

# Example 1: Using a computed goto:

from goto import goto, label

label .getinput

i = raw_input("Enter either 'a', 'b' or 'c', or any other letter to quit: ")

if i in ('a', 'b', 'c'):

    goto *i

else:

    goto .quit

label .a

print "You typed 'a'"

goto .getinput

label .b

print "You typed 'b'"

goto .getinput

label .c

print "You typed 'c'"

goto .getinput

label .quit

print "Finished\n"

# Example 2: Restarting a loop:

from goto import goto, label

label .start

for i in range(1, 5):

    print i

    if i == 3:

        try:

            output = message

        except NameError:

            print "Oops!  Start again please."

            message = "Hello world"

            goto .start

print output, "\n"

# Exception Program

# Example 3: When a label goes missing

from goto import goto, label

label .isreal

goto .notreal      # Raises a MissingLabelError exception.