correct formation of if elif else statement in Python

Question

Please find the below code block in python 2.7.

for i in range(len(p_routes)):
    if len(p_routes[i]) > 2 :
        if p_routes[i][2] == 'No Backup':   
            K = K + 1
            for z in range(len(p_routes[i])):
                nbup.write(K + 1 , z , p_routes[i][z])

        elif p_routes[i][0][0] == 'E' :
            L = L + 1
            for z in range(len(p_routes[i])):
                ex.write(L, z , (p_routes[i][z])

        elif p_routes[i][0][0] == 'G':
            M = M + 1
            for z in range(len(p_routes[i]))
                gh.write(M ,z, p_routes[i][z])

    else len(p_routes[i]) < 2:
        pass
        print "\nFor some reason. "

Well, I am getting an syntax error saying elif p_routes[i][0][0] == 'G': . I couldn't figure out why this error is coming as I believe there is no syntax error in this line.

The ex and gh are two excel sheet variable created before this code block. And p_routes is a list of list of 2 degrees. The format is like p_routes = [['prov1' , 'address1' , 'No Backup'] , ['prov2', 'address2', 'Back1', 'Back2' ]]

You might have understood, that the inner list length is a variable size. Any advise would be much appreciated. Sorry for the silly question but I did a lot of searching and re-formatting my if..else block in number of ways. But every time I am getting this error.

By the way previously the syntax error was with L = L + 1. Funny! Then I changed the type of L by L = int(L). Now, that error is gone.

You will be getting an error on the else statement as well, else doesn't have a condition, it's what is done if all other conditions are false. Besides, both pass and a print statement? — Some programmer dude
– Some programmer dude, Commented Sep 16, 2015 at 5:28
It is syntax error ex.write(L, z , (p_routes[i][z]) should be this ex.write(L, z , (p_routes[i][z])) and there are many other errors — The6thSense
– The6thSense, Commented Sep 16, 2015 at 5:28
Thanks a lot mate for your quick and to the point answer. As you pointed out, yes this was the issue indeed. — Neo
– Neo, Commented Sep 18, 2015 at 5:54

The6thSense · Accepted Answer · 2015-09-16 06:00:40Z

1

Notes:

Never forget to close the ( with )

Else will execute if none of the above case condition was right so you should not give any condition to else statement

Don't forget : in if else for.....

Changes to your code:

for i in range(len(p_routes)):
    if len(p_routes[i]) > 2 :
        if p_routes[i][2] == 'No Backup':   
            K = K + 1
            for z in range(len(p_routes[i])):
                nbup.write(K + 1 , z , p_routes[i][z])

        elif p_routes[i][0][0] == 'E' :
            L = L + 1
            for z in range(len(p_routes[i])):
                ex.write(L, z , (p_routes[i][z]))

        elif p_routes[i][0][0] == 'G':
            M = M + 1
            for z in range(len(p_routes[i])):
                gh.write(M ,z, p_routes[i][z])

    else :
        pass
        print "\nFor some reason. "

answered Sep 16, 2015 at 6:00

The6thSense

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The6thSense · Accepted Answer · 2015-09-16 09:15:27Z

1

First off as Vignesh pointed out, your error is actually on the previous line as you forgot to close your parenthesis ( )

Second, the else clause for the if, elif, else structure does not require a check. Here is a video I made a while ago with how selection works in python linked to relevant time

(May not be relevant) Also keep in mind with your current logic, what happens if: len(p_routes[i]) is 2? you currently only check if it's less than two or greater than 2.

edited Sep 16, 2015 at 9:15

The6thSense

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answered Sep 16, 2015 at 6:10

DrapsTV

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1 Comment

Neo Over a year ago

Thanks mate for pointing out the possible bug. But it was kept intentionally as the variable mentioned here would be a output from some ssh commands and as the way I did the regex filtering, the possible outcome could only be <2 or >2.

Martin Evans · Accepted Answer · 2015-09-16 06:15:56Z

0

With syntax errors, it is always wise to have a look at the preceding line to make sure it is also correct. As you missed the closing ), Python kept looking for it on the next line.

There are a number of areas you could make the code a bit cleaner. For example it is not necessary to keep using range(len(x)) when you can just iterate over the list itself.

Hopefully you find the following ideas helpful:

for route in p_routes:
    length = len(route)

    if length > 2 :
        if route[2] == 'No Backup':   
            K += 1
            for z in range(length):
                nbup.write(K + 1, z, p_routes[i][z])

        elif route[0][0] == 'E':
            L += 1
            for z in range(length):
                ex.write(L, z, (p_routes[i][z]))

        elif route[0][0] == 'G':
            M += 1
            for z in range(length):
                gh.write(M ,z, p_routes[i][z])

    elif length == 2:
        print "It is equal to 2"
    else:
        print "It must be less than 2"

Note, if x > 2 followed by an else, the else would imply the value is <= 2.

It is also possible to add one to a variable as follows: L += 1, this is shorthand for L = L + 1.

answered Sep 16, 2015 at 6:15

Martin Evans

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1 Comment

Neo Over a year ago

Thanks a lot for your valuable suggestion.. Yes the syntax error was coming from the non closing bracket indeed. I also figured out just after posting but was too bz doing the rest of the code completion. Now its working fine. :-)

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