Breaking out of a while loop when hitting a duplicate

I have this code:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    while True:

        last_item = ""



        for item in step:

            if item != last_item: 

                print(item)

                last_item = item

            else:

                break

The desired result is for the loop to print A, then B, then C, but when hitting the first duplicate C it should move on to printing D, then E, then F, and then stop when hitting the first duplicate F.

This is a minimal reproducible example of a loop to be used in a web scraping job, so solutions that involve doing set(steps)or other operations on the example steps as such will not solve it. My question has to to with the architecture of the loop.

asked Jan 1 at 10:14

DIGSUM

62851626

Can you have a set of seen elements and the print only if not in seen?

– Daniel Mesejo
Jan 1 at 10:18

2

Comment while true and it should work in the way you want. Check this

– Rajen Raiyarela
Jan 1 at 10:20

What is going wrong with your code at the moment? If you move the while loop outside for step in steps: then it seems to work as expected.

– Ari Cooper-Davis
Jan 1 at 10:20

add a comment |

I have this code:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    while True:

        last_item = ""



        for item in step:

            if item != last_item: 

                print(item)

                last_item = item

            else:

                break

asked Jan 1 at 10:14

DIGSUM

62851626

Can you have a set of seen elements and the print only if not in seen?

– Daniel Mesejo
Jan 1 at 10:18

2

Comment while true and it should work in the way you want. Check this

– Rajen Raiyarela
Jan 1 at 10:20

What is going wrong with your code at the moment? If you move the while loop outside for step in steps: then it seems to work as expected.

– Ari Cooper-Davis
Jan 1 at 10:20

add a comment |

I have this code:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    while True:

        last_item = ""



        for item in step:

            if item != last_item: 

                print(item)

                last_item = item

            else:

                break

asked Jan 1 at 10:14

DIGSUM

62851626

I have this code:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    while True:

        last_item = ""



        for item in step:

            if item != last_item: 

                print(item)

                last_item = item

            else:

                break

python

asked Jan 1 at 10:14

DIGSUM

62851626

asked Jan 1 at 10:14

DIGSUM

62851626

asked Jan 1 at 10:14

DIGSUM

62851626

asked Jan 1 at 10:14

DIGSUM

62851626

asked Jan 1 at 10:14

DIGSUM

62851626

Can you have a set of seen elements and the print only if not in seen?

– Daniel Mesejo
Jan 1 at 10:18

2

Comment while true and it should work in the way you want. Check this

– Rajen Raiyarela
Jan 1 at 10:20

What is going wrong with your code at the moment? If you move the while loop outside for step in steps: then it seems to work as expected.

– Ari Cooper-Davis
Jan 1 at 10:20

add a comment |

Can you have a set of seen elements and the print only if not in seen?

– Daniel Mesejo
Jan 1 at 10:18

2

Comment while true and it should work in the way you want. Check this

– Rajen Raiyarela
Jan 1 at 10:20

What is going wrong with your code at the moment? If you move the while loop outside for step in steps: then it seems to work as expected.

– Ari Cooper-Davis
Jan 1 at 10:20

Can you have a set of seen elements and the print only if not in seen?

– Daniel Mesejo
Jan 1 at 10:18

Comment while true and it should work in the way you want. Check this

– Rajen Raiyarela
Jan 1 at 10:20

What is going wrong with your code at the moment? If you move the while loop outside for step in steps: then it seems to work as expected.

– Ari Cooper-Davis
Jan 1 at 10:20

add a comment |

4 Answers
4

active

oldest

votes

Option with while loop, accessing objects by index:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



i = 0

ii = 0

memo = 

res = 

while True:

  if i == len(steps): break

  e = steps[i][ii]

  if e in memo:

    res.append(memo)

    memo = 

    ii = 0

    i += 1

  else:

    memo.append(e)

    print(e)

    ii += 1

It prints out:

# A

# B

# C

# D

# E

# F

While res value is:

print(res) #=> [['A', 'B', 'C'], ['D', 'E', 'F']]

answered Jan 1 at 10:45

iGian

4,4842625

add a comment |

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:

  last_item = ""



  for item in step:

      if item != last_item: 

          print(item)

          last_item = item

      else:

          break

When you keep while true and break is encountered from inner for loop, control will never pass to outer for loop for getting next item

(['D', 'E', 'F', 'F', 'F'])

in outer list, creating infinite loop.

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

add a comment |

You do not need while True. Except for that part your code works as expected:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    # while True:

        last_item = ""



        for item in step:

            if item != last_item:

                print(item)

                last_item = item

            else:

                break

Output:

A

B

C

D

E

F

answered Jan 1 at 10:25

BlackBeard

5,45242640

add a comment |

Remove this while loop from your code. [break] below works in this loop. To achieve your desired output, [break] need to break the for loop above.

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



# while True:

    last_item = ""



    for item in step:

        if item != last_item:

            print(item)

            last_item = item

        else:

            break

answered Jan 1 at 10:45

Aravind Kumar

add a comment |

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4 Answers
4

active

oldest

votes

4 Answers
4

active

oldest

votes

Option with while loop, accessing objects by index:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



i = 0

ii = 0

memo = 

res = 

while True:

  if i == len(steps): break

  e = steps[i][ii]

  if e in memo:

    res.append(memo)

    memo = 

    ii = 0

    i += 1

  else:

    memo.append(e)

    print(e)

    ii += 1

It prints out:

# A

# B

# C

# D

# E

# F

While res value is:

print(res) #=> [['A', 'B', 'C'], ['D', 'E', 'F']]

answered Jan 1 at 10:45

iGian

4,4842625

add a comment |

Option with while loop, accessing objects by index:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



i = 0

ii = 0

memo = 

res = 

while True:

  if i == len(steps): break

  e = steps[i][ii]

  if e in memo:

    res.append(memo)

    memo = 

    ii = 0

    i += 1

  else:

    memo.append(e)

    print(e)

    ii += 1

It prints out:

# A

# B

# C

# D

# E

# F

While res value is:

print(res) #=> [['A', 'B', 'C'], ['D', 'E', 'F']]

answered Jan 1 at 10:45

iGian

4,4842625

add a comment |

Option with while loop, accessing objects by index:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



i = 0

ii = 0

memo = 

res = 

while True:

  if i == len(steps): break

  e = steps[i][ii]

  if e in memo:

    res.append(memo)

    memo = 

    ii = 0

    i += 1

  else:

    memo.append(e)

    print(e)

    ii += 1

It prints out:

# A

# B

# C

# D

# E

# F

While res value is:

print(res) #=> [['A', 'B', 'C'], ['D', 'E', 'F']]

answered Jan 1 at 10:45

iGian

4,4842625

Option with while loop, accessing objects by index:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



i = 0

ii = 0

memo = 

res = 

while True:

  if i == len(steps): break

  e = steps[i][ii]

  if e in memo:

    res.append(memo)

    memo = 

    ii = 0

    i += 1

  else:

    memo.append(e)

    print(e)

    ii += 1

It prints out:

# A

# B

# C

# D

# E

# F

While res value is:

print(res) #=> [['A', 'B', 'C'], ['D', 'E', 'F']]

answered Jan 1 at 10:45

iGian

4,4842625

answered Jan 1 at 10:45

iGian

4,4842625

answered Jan 1 at 10:45

iGian

4,4842625

answered Jan 1 at 10:45

iGian

4,4842625

add a comment |

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:

  last_item = ""



  for item in step:

      if item != last_item: 

          print(item)

          last_item = item

      else:

          break

When you keep while true and break is encountered from inner for loop, control will never pass to outer for loop for getting next item

(['D', 'E', 'F', 'F', 'F'])

in outer list, creating infinite loop.

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

add a comment |

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:

  last_item = ""



  for item in step:

      if item != last_item: 

          print(item)

          last_item = item

      else:

          break

When you keep while true and break is encountered from inner for loop, control will never pass to outer for loop for getting next item

(['D', 'E', 'F', 'F', 'F'])

in outer list, creating infinite loop.

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

add a comment |

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:

  last_item = ""



  for item in step:

      if item != last_item: 

          print(item)

          last_item = item

      else:

          break

When you keep while true and break is encountered from inner for loop, control will never pass to outer for loop for getting next item

(['D', 'E', 'F', 'F', 'F'])

in outer list, creating infinite loop.

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:

  last_item = ""



  for item in step:

      if item != last_item: 

          print(item)

          last_item = item

      else:

          break

When you keep while true and break is encountered from inner for loop, control will never pass to outer for loop for getting next item

(['D', 'E', 'F', 'F', 'F'])

in outer list, creating infinite loop.

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

edited Jan 1 at 10:30

Rajen Raiyarela

3,80031534

answered Jan 1 at 10:21

Nafees Anwar

344115

answered Jan 1 at 10:21

Nafees Anwar

344115

answered Jan 1 at 10:21

Nafees Anwar

344115

add a comment |

You do not need while True. Except for that part your code works as expected:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    # while True:

        last_item = ""



        for item in step:

            if item != last_item:

                print(item)

                last_item = item

            else:

                break

Output:

A

B

C

D

E

F

answered Jan 1 at 10:25

BlackBeard

5,45242640

add a comment |

You do not need while True. Except for that part your code works as expected:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    # while True:

        last_item = ""



        for item in step:

            if item != last_item:

                print(item)

                last_item = item

            else:

                break

Output:

A

B

C

D

E

F

answered Jan 1 at 10:25

BlackBeard

5,45242640

add a comment |

You do not need while True. Except for that part your code works as expected:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    # while True:

        last_item = ""



        for item in step:

            if item != last_item:

                print(item)

                last_item = item

            else:

                break

Output:

A

B

C

D

E

F

answered Jan 1 at 10:25

BlackBeard

5,45242640

You do not need while True. Except for that part your code works as expected:

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



    # while True:

        last_item = ""



        for item in step:

            if item != last_item:

                print(item)

                last_item = item

            else:

                break

Output:

A

B

C

D

E

F

answered Jan 1 at 10:25

BlackBeard

5,45242640

answered Jan 1 at 10:25

BlackBeard

5,45242640

answered Jan 1 at 10:25

BlackBeard

5,45242640

answered Jan 1 at 10:25

BlackBeard

5,45242640

add a comment |

Remove this while loop from your code. [break] below works in this loop. To achieve your desired output, [break] need to break the for loop above.

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



# while True:

    last_item = ""



    for item in step:

        if item != last_item:

            print(item)

            last_item = item

        else:

            break

answered Jan 1 at 10:45

Aravind Kumar

add a comment |

Remove this while loop from your code. [break] below works in this loop. To achieve your desired output, [break] need to break the for loop above.

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



# while True:

    last_item = ""



    for item in step:

        if item != last_item:

            print(item)

            last_item = item

        else:

            break

answered Jan 1 at 10:45

Aravind Kumar

add a comment |

Remove this while loop from your code. [break] below works in this loop. To achieve your desired output, [break] need to break the for loop above.

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



# while True:

    last_item = ""



    for item in step:

        if item != last_item:

            print(item)

            last_item = item

        else:

            break

answered Jan 1 at 10:45

Aravind Kumar

Remove this while loop from your code. [break] below works in this loop. To achieve your desired output, [break] need to break the for loop above.

steps = [['A', 'B', 'C', 'C', 'C'], ['D', 'E', 'F', 'F', 'F']]



for step in steps:



# while True:

    last_item = ""



    for item in step:

        if item != last_item:

            print(item)

            last_item = item

        else:

            break

answered Jan 1 at 10:45

Aravind Kumar

answered Jan 1 at 10:45

Aravind Kumar

answered Jan 1 at 10:45

Aravind Kumar

answered Jan 1 at 10:45

Aravind Kumar

add a comment |

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