[python] python for increment inner loop

How to increment the outer iterator from the inner loop?

To be more precise:

  for i in range(0,6):
    print i
    for j in range(0,5):
      i = i+2

I am getting

0
1
2
3
4
5

, but I want 0,2,4

Above is the simpilfied idea what I want to acheive.

Here is my Java code:

str1="ababa"
str2="aba"
for(int i =0; i < str1.length; i++)
  for(int j =0; j < str2.length; j++)
       if str1[i+j]!=str[j]
           break;
       if( j ==str2.length -1)
           i=i+str2.length;

for a in range(1):

    for b in range(3):
        a = b*2
        print(a)

As per your question, you want to iterate the outer loop with help of the inner loop.

1. In outer loop, we are iterating the inner loop 1 time.

2. In the inner loop, we are iterating the 3 digits which are in the multiple of 2, starting from 0.

   Output:
   0
   2
   4
   

You might just be better of using while loops rather than for loops for this. I translated your code directly from the java code.

str1 = "ababa"
str2 = "aba"
i = 0

while i < len(str1):
  j = 0
  while j < len(str2):
    if not str1[i+j] == str1[j]:
      break
    if j == (len(str2) -1):
      i += len(str2)
    j+=1  
  i+=1

In python, for loops iterate over iterables, instead of incrementing a counter, so you have a couple choices. Using a skip flag like Artsiom recommended is one way to do it. Another option is to make a generator from your range and manually advance it by discarding an element using next().

iGen = (i for i in range(0, 6))
for i in iGen:
    print i
    if not i % 2:
        iGen.next()

But this isn't quite complete because next() might throw a StopIteration if it reaches the end of the range, so you have to add some logic to detect that and break out of the outer loop if that happens.

In the end, I'd probably go with aw4ully's solution with the while loops.

I read all the above answers and those are actually good.

look at this code:

for i in range(1, 4):
    print("Before change:", i)
    i = 20 # changing i variable
    print("After change:", i) # this line will always print 20

When we execute above code the output is like below,

Before Change: 1
After change: 20
Before Change: 2
After change: 20
Before Change: 3
After change: 20

in python for loop is not trying to increase i value. for loop is just assign values to i which we gave. Using range(4) what we are doing is we give the values to for loop which need assign to the i.

You can use while loop instead of for loop to do same thing what you want,

i = 0
while i < 6:
    print(i)
    j = 0
    while j < 5:
        i += 2 # to increase `i` by 2

This will give,

0
2
4

Thank you !