CODEWITHSUNDEEP
pythonpython-2.7python-3.x
Sharanabasu Angadi
Sharanabasu Angadi

Reputation: 4372

python loop back to previous element in for loop

How can I perform below code in python I am new to python and getting troubled, please could someone help

objects = [............] // Array
for (i=0; i<objects.length(); i++) {
    if(readElement(objects[i])){
        //do something
    } else {
      i--; // so that same object is given in next iteration and readElement cant get true
    }
}

Upvotes: 2

Views: 2107

Answers (4)

benjaminz
benjaminz

Reputation: 3228

I was looking for the same thing, but I ended up writing a while loop, and manage the index myself.

That said, your code can be implemented in Python as:

objects = [............] # Array
idx = 0

while idx < len(objects):
    if readElement(objects[idx]):
        # do hacky yet cool stuff
    elif idx != 0:
        idx -= 1 # THIS is what you hoped to do inside the for loop
    else:
        # some conditions that we haven't thought about how to handle

Upvotes: 0

Marvo
Marvo

Reputation: 520

Your code is iterating through a list of objects and repeats "readElement" until it returns "True", in which case you call "do something". Well, you could just write that down:

for object in objects:
    while not readElement(object): pass
    dosomething()

[Edit: the first version of this answer inverted the logic, sorry]

Upvotes: -1

Shruti Srivastava
Shruti Srivastava

Reputation: 398

You can try this out

 objects = ["ff","gg","hh","ii","jj","kk"] # Array
 count =0
 for i in objects: # (i=0; i<objects.length(); i++) {
    if i:
        print i
    else :
        print objects[count-1]
    count =+1

Upvotes: 0

AvidLearner
AvidLearner

Reputation: 4163

Have you considered using recursion?

def func(objects,i):
    if i == len(objects):
        return
    if readElement(objects[i]){
        #do something
        func(objects,i+1)
    else 
        func(objects,i)--; # so that same object is given in next iteration and readElement cant get true
    }
objects = [............] # list
func(objects,0)

Else, you can do this(very non-Pythonic, but using for loops only as you requested):

objects = [............] # Array
func(objects,0)
M = 10E6 # The maximum number of calls you think is needed to readElement(objects[i])
for i in xrange(objects)
    for j in xrange(M):
        if readElement(objects[i]):
            #do something
            break

Upvotes: 2

Related Questions