Code works in Java but not Python?

Question

This code seems to work in Java, but when I convert it to Python, it exceeds the maximum recursion depth and exits.. Not sure what the difference is. They look like they function identically to me.

Java version:

public String addCommas(String number)
{
  if(number.length < 4
  {
    return number;
  }
  return addCommas(number.subString(0, number.length - 3)) + "," + number.subString(number.length - 3, number.length);
}

Python version:

def addCommas(number):
    number = str(number)
    if len(number) < 4:
        return number
    else:
        return addCommas(number[:len(number) - 3] + ',' + number[len(number) - 3:])

Thanks in advance for any help!

Removing the Java tag assuming you don't want the answer in Java. — Peter Lawrey
– Peter Lawrey, Commented Jul 30, 2016 at 9:44
Your parentheses are different. The call to addCommas should end after number[:len(number) - 3] but it doesn't. return addCommas(number[:len(number) - 3]) + ',' + number[len(number) - 3:] — Aran-Fey
– Aran-Fey, Commented Jul 30, 2016 at 9:47

Marcy · Accepted Answer · 2016-07-30 09:48:01Z

1

The difference is in the last line.

 return addCommas(number.subString(0, number.length - 3)) + "," + number.subString(number.length - 3, number.length);

This calls addCommas on the first substring only (which reduces the length of the string parameter for the next call by 3) and then appends a comma and the last three digits to its result.

 return addCommas(number[:len(number) - 3] + ',' + number[len(number) - 3:])

This on the other hand first adds a comma and calls addCommas on the whole new string (which is even longer than the original, resulting in the infinite recursion loop).

 return addCommas(number[:len(number) - 3]) + ',' + number[len(number) - 3:]

This would work as it only calls addCommas on the first substring and adds the commas to the result of addCommas, the same way the Java code does it.

answered Jul 30, 2016 at 9:48

Marcy

3,0261 gold badge27 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

rajashekarpula · Accepted Answer · 2016-07-30 10:08:44Z

0

The difference is in the last line

Java : return addCommas(number.subString(0, number.length - 3)) + "," + number.subString(number.length - 3, number.length);

Python : return addCommas(number[:len(number) - 3] + ',' + number[len(number) - 3:])

are not same. If you observe in java you are calling addCommas and then appending comma and a string. Whereas in python you are only calling addCommas function.This will lead to infinite loop. Just do it same as in java.

return addCommas(number[:len(number) - 3] + ',' + number[len(number) - 3:])

answered Jul 30, 2016 at 10:08

rajashekarpula

111 silver badge2 bronze badges

Collectives™ on Stack Overflow

Code works in Java but not Python?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related