round() in Python

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11
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I'm currently learning python with pycharm as IDE. While using the round() function I noticed that I get two different results depending on wether I don't explicitly choose the number of decimal places to include or choosing the number to be 0.

x = 4.1
print(round(x))
print(round(x, 0))

It prints the following:

4
4.0

What is the difference?

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

I get 4.0 in both cases (python 3.5)
â€“Â taras
1 hour ago

2

+1 I was surprised by the downvote. This is a good question, with runnable code, probing a counterintuitive edge-case. I certainly learned something from this. Thanks, Peter.
â€“Â Bill Cheatham
1 hour ago

2

@taras: nope, round(4.1) in Python 3.5 produces 4, only round(4.1, 0) produces 4.0. Do triple-check your Python versions. Use import sys; print(sys.version_info) from inside Python if you have to, because the behaviour you are reporting is specific to Python two. The round() function documentation for Python 3 covers this case explicitly: If ndigits is omitted or is None, it returns the nearest integer to its input..
â€“Â Martijn Pietersâ™¦
1 hour ago

@MartijnPieters, thank you for pointing it out. Apparently, I've checked it using 2.7 thinking I was running 3.5.
â€“Â taras
39 mins ago

add a commentÂ |Â

up vote
11
down vote

favorite

x = 4.1
print(round(x))
print(round(x, 0))

It prints the following:

4
4.0

What is the difference?

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

I get 4.0 in both cases (python 3.5)
â€“Â taras
1 hour ago

2

+1 I was surprised by the downvote. This is a good question, with runnable code, probing a counterintuitive edge-case. I certainly learned something from this. Thanks, Peter.
â€“Â Bill Cheatham
1 hour ago

2

@taras: nope, round(4.1) in Python 3.5 produces 4, only round(4.1, 0) produces 4.0. Do triple-check your Python versions. Use import sys; print(sys.version_info) from inside Python if you have to, because the behaviour you are reporting is specific to Python two. The round() function documentation for Python 3 covers this case explicitly: If ndigits is omitted or is None, it returns the nearest integer to its input..
â€“Â Martijn Pietersâ™¦
1 hour ago

@MartijnPieters, thank you for pointing it out. Apparently, I've checked it using 2.7 thinking I was running 3.5.
â€“Â taras
39 mins ago

add a commentÂ |Â

up vote
11
down vote

favorite

x = 4.1
print(round(x))
print(round(x, 0))

It prints the following:

4
4.0

What is the difference?

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

x = 4.1
print(round(x))
print(round(x, 0))

It prints the following:

4
4.0

What is the difference?

python python-3.x rounding

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

edited 1 hour ago

Martijn Pietersâ™¦

681k12323332192

asked 1 hour ago

Peter Hofer

612

New contributor

asked 1 hour ago

Peter Hofer

612

asked 1 hour ago

Peter Hofer

612

New contributor

Peter Hofer is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

I get 4.0 in both cases (python 3.5)
â€“Â taras
1 hour ago

2

+1 I was surprised by the downvote. This is a good question, with runnable code, probing a counterintuitive edge-case. I certainly learned something from this. Thanks, Peter.
â€“Â Bill Cheatham
1 hour ago

2

@taras: nope, round(4.1) in Python 3.5 produces 4, only round(4.1, 0) produces 4.0. Do triple-check your Python versions. Use import sys; print(sys.version_info) from inside Python if you have to, because the behaviour you are reporting is specific to Python two. The round() function documentation for Python 3 covers this case explicitly: If ndigits is omitted or is None, it returns the nearest integer to its input..
â€“Â Martijn Pietersâ™¦
1 hour ago

@MartijnPieters, thank you for pointing it out. Apparently, I've checked it using 2.7 thinking I was running 3.5.
â€“Â taras
39 mins ago

add a commentÂ |Â

I get 4.0 in both cases (python 3.5)
â€“Â taras
1 hour ago

2

+1 I was surprised by the downvote. This is a good question, with runnable code, probing a counterintuitive edge-case. I certainly learned something from this. Thanks, Peter.
â€“Â Bill Cheatham
1 hour ago

2

@taras: nope, round(4.1) in Python 3.5 produces 4, only round(4.1, 0) produces 4.0. Do triple-check your Python versions. Use import sys; print(sys.version_info) from inside Python if you have to, because the behaviour you are reporting is specific to Python two. The round() function documentation for Python 3 covers this case explicitly: If ndigits is omitted or is None, it returns the nearest integer to its input..
â€“Â Martijn Pietersâ™¦
1 hour ago

@MartijnPieters, thank you for pointing it out. Apparently, I've checked it using 2.7 thinking I was running 3.5.
â€“Â taras
39 mins ago

I get 4.0 in both cases (python 3.5)
â€“Â taras
1 hour ago

+1 I was surprised by the downvote. This is a good question, with runnable code, probing a counterintuitive edge-case. I certainly learned something from this. Thanks, Peter.
â€“Â Bill Cheatham
1 hour ago

@taras: nope, round(4.1) in Python 3.5 produces 4, only round(4.1, 0) produces 4.0. Do triple-check your Python versions. Use import sys; print(sys.version_info) from inside Python if you have to, because the behaviour you are reporting is specific to Python two. The round() function documentation for Python 3 covers this case explicitly: If ndigits is omitted or is None, it returns the nearest integer to its input..
â€“Â Martijn Pietersâ™¦
1 hour ago

@MartijnPieters, thank you for pointing it out. Apparently, I've checked it using 2.7 thinking I was running 3.5.
â€“Â taras
39 mins ago

add a commentÂ |Â

3 Answers
3

active

oldest

votes

up vote
10
down vote

When you specify the number of decimals, even if that number is 0, you are calling the version of the method that returns a float. So it is normal that you get that result.

answered 1 hour ago

Osuman AAA

277111

2

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

add a commentÂ |Â

up vote
2
down vote

The round() function in python takes 2 parameters

1) number - number to be rounded
2) number of digits (Optional) - the number of digits up to which the given number is to be rounded.

Whenever you use the second parameter, Python automatically converts the data type of the return value to float. If you don't use the second optional parameter then the data type remains an integer.

Therefore, it is 4.0 when the parameter is passed and 4 when it isn't.

answered 1 hour ago

codelyzer

158114

add a commentÂ |Â

up vote
2
down vote

the round function returns an integer if the second argument is not specified else the return value has the same type as that of the first argument

>>> help(round)
Help on built-in function round in module builtins:

round(number, ndigits=None)
 Round a number to a given precision in decimal digits.

 The return value is an integer if ndigits is omitted or None. Otherwise
 the return value has the same type as the number. ndigits may be negative.

so if the arguments passed are an integer and a zero the return value will be an integer type

>>> round(100, 0)
100
>>> round(100, 1)
100

For the sake of completeness

negative numbers are used for rounding before the decimal place

>>> round(124638, -2)
124600
>>> round(15432.346, -2)
15400.0

answered 14 mins ago

Aniket Navlur

16419

add a commentÂ |Â

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3 Answers
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active

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3 Answers
3

active

oldest

votes

up vote
10
down vote

When you specify the number of decimals, even if that number is 0, you are calling the version of the method that returns a float. So it is normal that you get that result.

answered 1 hour ago

Osuman AAA

277111

2

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

add a commentÂ |Â

up vote
10
down vote

When you specify the number of decimals, even if that number is 0, you are calling the version of the method that returns a float. So it is normal that you get that result.

answered 1 hour ago

Osuman AAA

277111

2

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

add a commentÂ |Â

up vote
10
down vote

When you specify the number of decimals, even if that number is 0, you are calling the version of the method that returns a float. So it is normal that you get that result.

answered 1 hour ago

Osuman AAA

277111

When you specify the number of decimals, even if that number is 0, you are calling the version of the method that returns a float. So it is normal that you get that result.

answered 1 hour ago

Osuman AAA

277111

answered 1 hour ago

Osuman AAA

277111

answered 1 hour ago

Osuman AAA

277111

answered 1 hour ago

Osuman AAA

277111

2

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

add a commentÂ |Â

2

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

Yep, pretty straightforward. Just like it says in help(round), it "returns an int when called with one argument, otherwise the same type as the number."
â€“Â Kevin
1 hour ago

Might want to link to the docs and quote the first sentence.
â€“Â kabanus
58 mins ago

add a commentÂ |Â

up vote
2
down vote

The round() function in python takes 2 parameters

1) number - number to be rounded
2) number of digits (Optional) - the number of digits up to which the given number is to be rounded.

Whenever you use the second parameter, Python automatically converts the data type of the return value to float. If you don't use the second optional parameter then the data type remains an integer.

Therefore, it is 4.0 when the parameter is passed and 4 when it isn't.

answered 1 hour ago

codelyzer

158114

add a commentÂ |Â

up vote
2
down vote

The round() function in python takes 2 parameters

1) number - number to be rounded
2) number of digits (Optional) - the number of digits up to which the given number is to be rounded.

Whenever you use the second parameter, Python automatically converts the data type of the return value to float. If you don't use the second optional parameter then the data type remains an integer.

Therefore, it is 4.0 when the parameter is passed and 4 when it isn't.

answered 1 hour ago

codelyzer

158114

add a commentÂ |Â

up vote
2
down vote

The round() function in python takes 2 parameters

1) number - number to be rounded
2) number of digits (Optional) - the number of digits up to which the given number is to be rounded.

Whenever you use the second parameter, Python automatically converts the data type of the return value to float. If you don't use the second optional parameter then the data type remains an integer.

Therefore, it is 4.0 when the parameter is passed and 4 when it isn't.

answered 1 hour ago

codelyzer

158114

The round() function in python takes 2 parameters

1) number - number to be rounded
2) number of digits (Optional) - the number of digits up to which the given number is to be rounded.

Whenever you use the second parameter, Python automatically converts the data type of the return value to float. If you don't use the second optional parameter then the data type remains an integer.

Therefore, it is 4.0 when the parameter is passed and 4 when it isn't.

answered 1 hour ago

codelyzer

158114

answered 1 hour ago

codelyzer

158114

answered 1 hour ago

codelyzer

158114

answered 1 hour ago

codelyzer

158114

add a commentÂ |Â

up vote
2
down vote

the round function returns an integer if the second argument is not specified else the return value has the same type as that of the first argument

>>> help(round)
Help on built-in function round in module builtins:

round(number, ndigits=None)
 Round a number to a given precision in decimal digits.

 The return value is an integer if ndigits is omitted or None. Otherwise
 the return value has the same type as the number. ndigits may be negative.

so if the arguments passed are an integer and a zero the return value will be an integer type

>>> round(100, 0)
100
>>> round(100, 1)
100

For the sake of completeness

negative numbers are used for rounding before the decimal place

>>> round(124638, -2)
124600
>>> round(15432.346, -2)
15400.0

answered 14 mins ago

Aniket Navlur

16419

add a commentÂ |Â

up vote
2
down vote

the round function returns an integer if the second argument is not specified else the return value has the same type as that of the first argument

>>> help(round)
Help on built-in function round in module builtins:

round(number, ndigits=None)
 Round a number to a given precision in decimal digits.

 The return value is an integer if ndigits is omitted or None. Otherwise
 the return value has the same type as the number. ndigits may be negative.

so if the arguments passed are an integer and a zero the return value will be an integer type

>>> round(100, 0)
100
>>> round(100, 1)
100

For the sake of completeness

negative numbers are used for rounding before the decimal place

>>> round(124638, -2)
124600
>>> round(15432.346, -2)
15400.0

answered 14 mins ago

Aniket Navlur

16419

add a commentÂ |Â

up vote
2
down vote

the round function returns an integer if the second argument is not specified else the return value has the same type as that of the first argument

>>> help(round)
Help on built-in function round in module builtins:

round(number, ndigits=None)
 Round a number to a given precision in decimal digits.

 The return value is an integer if ndigits is omitted or None. Otherwise
 the return value has the same type as the number. ndigits may be negative.

so if the arguments passed are an integer and a zero the return value will be an integer type

>>> round(100, 0)
100
>>> round(100, 1)
100

For the sake of completeness

negative numbers are used for rounding before the decimal place

>>> round(124638, -2)
124600
>>> round(15432.346, -2)
15400.0

answered 14 mins ago

Aniket Navlur

16419

the round function returns an integer if the second argument is not specified else the return value has the same type as that of the first argument

>>> help(round)
Help on built-in function round in module builtins:

round(number, ndigits=None)
 Round a number to a given precision in decimal digits.

 The return value is an integer if ndigits is omitted or None. Otherwise
 the return value has the same type as the number. ndigits may be negative.

so if the arguments passed are an integer and a zero the return value will be an integer type

>>> round(100, 0)
100
>>> round(100, 1)
100

For the sake of completeness

negative numbers are used for rounding before the decimal place

>>> round(124638, -2)
124600
>>> round(15432.346, -2)
15400.0

answered 14 mins ago

Aniket Navlur

16419

answered 14 mins ago

Aniket Navlur

16419

answered 14 mins ago

Aniket Navlur

16419

answered 14 mins ago

Aniket Navlur

16419

add a commentÂ |Â

Peter Hofer is a new contributor. Be nice, and check out our Code of Conduct.

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