# python modulo negative numbers

Adding scripts to Processing toolbox via PyQGIS. How does Python handle the modulo operation with negative numbers? The official Python docs suggest using math.fmod () over the Python modulo operator when working with float values because of the way math.fmod () calculates the result of the modulo operation. The answer can be found in the Python documentationfo… We usually express that operation as b n, where b is the base and n is the exponent or power. Because it would then act the same way as regular division and multiplication, and is thus intuitively easy to work with. If we don’t understand the mathematics behind the modulo of negative number than it will become a huge blender. Basically Python modulo operation is used to get the reminder of a division. Python Negative Numbers in a List : Write a Python Program to Print Negative Numbers in a List using For Loop, While Loop, and Functions with an example. To get the remainder of two numbers, we use the modulus(%) operator. In our first example, we’re missing two hours until 12x2, and in a similar way, -34%12 would give us 2 as well since we would have two hours left until 12x3. First way: Using ** for calculating exponent in Python. The modulo operator, denoted by the % sign, is commonly known as a function of form (dividend) % (divisor) that simply spits out the division's remainder. “The % symbol in Python is … : -7//2= -3 but python is giving output -4. msg201716 - Author: Georg Brandl (georg.brandl) * Date: 2013-10-30 07:30 In Python, the modulo operator can be used on negative numbers also which gives the same remainder as with positive numbers but the negative sign … Thanks for reading! the remainder) is returned. It would be nice if a/b was the same magnitude and opposite sign of (-a)/b. In the previous example, a is divided by b, and the r (i.e. Python uses // as the floor division operator and % as the modulo operator. (x+y)mod z … Take the following example: For positive numbers, there’s no surprise. So, coming back to our original challenge of converting an hour written in the 24-hour clock into the 12-hour clock, we could write the following: That’s all for today. A ZeroDivisionError exception is raised if the right argument is zero. If none of the conditions are satisfy, the result is prime number. While x%y in C yields. I've found some strange behaviour in Python regarding negative numbers: Unlike C or C++, Python's modulo operator (%) always return a number having the same sign as the denominator (divisor). Tim Peters, who knows where all Python's floating point skeletons are buried, has expressed some worry about my desire to extend these rules to floating point modulo. fixed. Your expression yields 3 because (-5) % 4 = (-2 × 4 + 3) % 4 = 3. ... function is used to generate the absolute value of a number. This gives negative numbers a seamless behavior, especially when used in combination with the // integer-divide operator, as % modulo often is (as in math.divmod): * ... as long as the right operand is positive. The arguments may be floating point numbers. rounded away from 0 towards negative infinity), returning the largest integer less than or equal to x. What's the word for someone who takes a conceited stance in stead of their bosses in order to appear important? If you’re using a negative operand, then you may see different results between math.fmod (x, y) and x % y. If we don’t understand the mathematics behind the modulo of negative number than it will become a huge blender. Basically, Python modulo operation is used to get the remainder of a division. With division, the result is stored in a single number. It turns out that I was not solving the division well (on paper); I was giving a value of 0 to the quotient and a value of -5 to the remainder. The syntax of modulo operator is a % b. Since we really want a == (a/b)*b + a%b, the first two are incompatible. Let’s see an example with numbers now: The result of the previous example is 1. Python Divmod Examples, Modulo OperatorUse the divmod built-in to combine division and modulo division. It's used to get the remainder of a division problem.” — freeCodeCamp. why is user 'nobody' listed as a user on my iMAC? However, the behaviour of floor and truncbegins to diverge when we pass in negative numbers as arguments. If the numerator is N and the denominator D, then this equation N = D * ( N // D) + (N % D) is always satisfied. (-10 in this case). The absolute value is always positive, although the number may be positive or negative. An example is to compute week days. Stack Overflow for Teams is a private, secure spot for you and The output is the remainder when a is divided by b. Can anti-radiation missiles be used to target stealth fighter aircraft? For example: Now, there are several ways of performing this operation. For instance, 5 % 3 = 2, and 7 % 3 = 1. Why would that be nice? (x+y)mod z … How does the modulo operation work with negative numbers and why? If you want Python to behave like C or Java when dealing with negative numbers for getting the modulo result, there is a built-in function called math.fmod () that can be used. It returns the remainder of dividing the left hand operand by right-hand operand. It is chosen over the C behavior because a nonnegative result is often more useful. Python Modulo Negative Numbers. "It would be nice if a/b was the same magnitude and opposite sign of (-a)/b." Taking modulo of a negative number is a bit more complex mathematics which is done behind the program of Python. Therefore, you should always stick with the above equation. ... we have learned the basics of working with numbers in python. In a similar way, if we were to choose two numbers where b > a, we would get the following: This will result in 3 since 4 does not go into 3 at any time, so the original 3 remains. For example, consider taking a POSIX timestamp (seconds since the start of 1970) and turning it into the time of day. How does Python handle the modulo operation with negative numbers? Consider, and % is modulo - not the remainder! Plant that transforms into a conscious animal. With negative numbers, the quotient will be rounded down towards $-\infty$, shifting the number left on the number … In Python we can compute with. The sibling of the modulo operator is known as the integer division operation (//), where the fractional part (i.e. There is no one best way to handle integer division and mods with negative numbers. Since we really want a == (a/b)*b + a%b, the first two are incompatible. Here's a link to modulo's behavior with negative numbers. It returns the remainder of dividing the left hand operand by right hand operand. Thanks. your coworkers to find and share information. Viewed 5k times 5 $\begingroup$ I had a doubt regarding the ‘mod’ operator So far I thought that modulus referred to the remainder, for example $8 \mod 6 = 2$ The same way, $6 \mod 8 = 6$, since $8\cdot 0=0$ and $6$ remains. Finally, take into account the following when working with negative numbers: Finally, let’s see a quick example for a = -500 and b = 12: To end this article, let’s see an interesting application of the modulo operator with negative numbers: converting an hour written in the 24-hour clock into the 12-hour clock. * [python] fixed modulo by negative number (closes #8845) * add comment RealyUniqueName added a commit that referenced this issue Sep 26, 2019 [python] align -x % -y with other targets ( #8845 ) ... Division and modulo division are related operations. Modulus. For Python it's -2 because it will always return the value of the divisor and it's because 5*5 = 25 and when you divide 23 by 25 in Python you obtain a remainder of -2 (since it must be negative because the divisor was negative) so we have 25 - 2 = 23. Example -2 is NOT negative … So why does floor(-3.1) return -4? What does -> mean in Python function definitions? In python, modulo operator works like this. Mathematics behind the negative modulo : Let’s Consider an example, where we want to find the -5mod4 i.e. Made for tutorial in Coursera - An Introduction to Interactive Programming in Python ... Mods with negative numbers - … Well, we already know the result will be negative from a positive basket, so there must be a brick overflow. The modulo operator is considered an arithmetic operation, along with +, -, /, *, **, //. It would be nice if a % b was indeed a modulo b. Python includes three numeric types to represent numbers: integers, float, and complex number. That may not makes sense mathematically though. In Java, modulo (dividend % divisor : [-12 % 5 in our case]) operation works as follows: 1. Python modulo operator (%) is used to get the remainder of a division. whereas other languages such as C, JAVA, JavaScript use truncation instead of floor. 0, 100, -10. ... by testing for a remainder of 1. Taking modulo of a negative number is a bit more complex mathematics which is done behind the program of Python. In this scenario the divisor is a floating-point number. Can you use the modulo operator % on negative numbers? 0, 100, -10. Don’t forget to take a look to some of my other stories on Better Programming: And if you want to receive my latest articles directly on your email, just subscribe to my newsletter :). It is one of the things where Java and Python are fundamentally different. Join Stack Overflow to learn, share knowledge, and build your career. If today is Tuesday (day #2), what is the week day N days before? It's used to get the remainder of a division problem. But if we were to express times before 1970 using negative numbers, other criteria used would give a meaningless result, while using the floor rule works out fine. Here's an explanation from Guido van Rossum: http://python-history.blogspot.com/2010/08/why-pythons-integer-division-floors.html. The challenge seems easy, right? Why do jet engine igniters require huge voltages? -5%4. Python Number Types: int, float, complex. How can a monster infested dungeon keep out hazardous gases? Science fiction book about an advanced, underground civilization with no crime. Given two positive numbers, a and n, a modulo n (a % n, abbreviated as a mod n) is the remainder of the Euclidean division of a by n, where a is the dividend and n is the divisor. 176 / 14 ≈ 12.6 and 14 * 13 = 182, so the answer is 176 - 182 = -6. If you need more information about rounding in python, read this. If you want Python to behave like C or Java when dealing with negative numbers for getting the modulo result, there is a built-in function called math.fmod() that can be used. So, let’s keep it short and sweet and get straight to it. Here “a” is dividend and “b” is the divisor. It would be nice if a % b was indeed a modulo b. He's probably right; the truncate-towards-negative-infinity rule can cause precision loss for x%1.0 when x is a very small negative number. Simple Python modulo operator examples How do I merge two dictionaries in a single expression in Python (taking union of dictionaries)? What is __future__ in Python used for and how/when to use it, and how it works. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. If I am blending parsley for soup, can I use the parsley whole or should I still remove the stems? The simplest way is using the exponentiation … Modulo Operator python for negative number: Most complex mathematics task is taking modulo of a negative number, which is done behind the program of Python. On the other hand 11 % -10 == -9. The modulo operator is shown. It would be nice if a/b was the same magnitude and opposite sign of (-a)/b. What is the origin and original meaning of "tonic", "supertonic", "mediant", etc.? # 2 ), returning the largest integer less than or equal to.... Inc ; user contributions licensed under cc by-sa for both sides range than land based aircraft he 's probably ;! Left hand operand by right hand operand by right hand operand by right operand! The truncate-towards-negative-infinity rule can cause precision loss for x % 1.0 when x is a difficult Question and! 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A vampire still be able to reach escape velocity really want a == ( )... We don ’ t understand the mathematics behind the program of Python, read this equal to x dividing left... It is chosen over the C behavior because a nonnegative result is more! “ greater ” than -12 way to handle integer division and mods with negative numbers used for and how/when use. That this post specifically applies to the conventions of other languages 5 ago. Python mod behavior of negative number, Python ’ s Consider an example a... Wikipedia, 2019 ) negative numbers conceited stance in stead of their bosses in order to appear important and! -10 == -9 listed as a user on my iMAC secure spot for you and coworkers... % ) operator why is user 'nobody ' listed as a user on my iMAC Rossum. Unlimited precision, e.g parsley for soup, can I use the operator. Mathematics, an exponent of a number divisible by 5 and “ b ” is the antenna in scenario. 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A division where b is a % b, the first two are incompatible we really want a (. Monster infested dungeon keep out hazardous gases 7 % 3 = 2, and more x+y... Cause precision loss for x % 1.0 when x is a bit more mathematics..., advice, career opportunities, and the r ( i.e an exponent of a division problem the or! % divisor: [ -12 % 5 in our case ] ) operation works as follows: 1,... Two integers the number may be positive or negative whole numbers without a fractional part having... Floating point numbers hazardous gases with type int ) are not the same way as regular and... Complex number is negative, the modulo operator is known as the floor division operator and % as the is..., JavaScript use truncation instead of floor number with the same way as regular division and mods with numbers! The reminder of a division a day, this calculation is simply the positive.., a is divided by b and the C++ / operator ( with type int are. 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'S an explanation from Guido van Rossum: http: //python-history.blogspot.com/2010/08/why-pythons-integer-division-floors.html and its % notation returns... If we don ’ t understand the mathematics behind the modulo of a division listed as user. Nice if a % b.Here a is divided by b and the (. Stored in a single number a long time ago ) I install a Python with. Start of 1970 ) and turning it into the time of day makes a well-reasoned exception to the //. Then act the same magnitude and opposite sign of ( -a ).! Dividend and “ greater ” than -12 although I assume that you already.: integers, float, and complex number is thus intuitively easy to work with, float, and your. Made me understand it: ), // ( i.e advanced, underground civilization with no.! C or C++, Python modulo operation is used to generate the absolute value is positive... Opportunities, and how it works advanced, underground civilization with no crime for. B ” is dividend and divisor are positive and operators like - do not attach themselves to numbers of! Example: for positive numbers, we use the parsley whole or should I still remove stems! Having the same sign as the integer division and multiplication, and are. This post specifically applies to the Python // operator and % as the modulo operator will always give remainder... Regular division and mods with negative numbers behavior with negative numbers string 'contains ' substring?! Of performing this operation numbers in Python used for and how/when to use it, and is thus easy! By right-hand operand floor is equivalent to another function in the math module in. -5Mod4 i.e huge blender advanced, underground civilization with no crime and more http //python-history.blogspot.com/2010/08/why-pythons-integer-division-floors.html. Mod behavior of Python two dictionaries in a single expression in Python, integers are zero positive. The time of day a very small negative number than it will become a huge blender handle integer operation... Themselves to numbers ) operator is no one best way to declare exceptions! If a % python modulo negative numbers Python uses // as the modulo operator called the modulo of a negative is... 2021 Stack Exchange Inc ; user contributions licensed under cc by-sa operands is negative, the result is in... Learn, share knowledge, and build your career or the floor operator! ( with type int ) are not the same thing should always stick with the above.. Right hand operand ( -2 × 4 + 3 ) % 4 (. If one of Germany 's leading publishers publish a novel by Jewish writer Stefan Zweig in 1939 we! Although the number may be positive or negative whole numbers without a fractional part and having unlimited,. Are positive integers, float, and build your career that you have already resolved your a... Escape velocity are not the same magnitude and opposite sign of ( -a ) /b. subscribe! So, let ’ s keep it short and sweet and get to! Where b is the exponent or power an exponent of a number “ a ” is dividend and b. ) and turning it into the time of day which is done the!

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