+34 973 224 921 femac@femac.org
Select Page

why is user 'nobody' listed as a user on my iMAC? This is something I learned recently and thought was worth sharing given that it quite surprised me and it’s a super-useful fact to learn. What's the word for someone who takes a conceited stance in stead of their bosses in order to appear important? “The % symbol in Python is called the Modulo Operator. (Although I assume that you have already resolved your concern a long time ago). In Python, integers are zero, positive or negative whole numbers without a fractional part and having unlimited precision, e.g. For positive numbers, floor is equivalent to another function in the math module called trunc. Thanks. The syntax of modulo operator is a % b. Modulo with Float. Essentially, it's so that a/b = q with remainder r preserves the relationships b*q + r = a and 0 <= r < b. Int. Not too many people understand that there is in fact no such thing as negative numbers. The basic syntax is: a % b For example, 23%2 will give us 11 and 15%12 will give us 3… exactly what we want! According to Guido van Rossum, the creator of Python, this criterion has some interesting applications. A weekly newsletter sent every Friday with the best articles we published that week. Here, the remainder will have the same sign as the divisor, so my divisor is positive that’s why the remainder is also positive vice versa. Basically, Python modulo operation is used to get the remainder of a division. 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. Stack Overflow for Teams is a private, secure spot for you and Science fiction book about an advanced, underground civilization with no crime. How do I merge two dictionaries in a single expression in Python (taking union of dictionaries)? Your expression yields 3 because (-5) % 4 = (-2 × 4 + 3) % 4 = 3. And the remainder (using the division from above): This calculation is maybe not the fastest but it's working for any sign combinations of x and y to achieve the same results as in C plus it avoids conditional statements. 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. Unlike C or C++, Python’s modulo operator always returns a number having the same sign as the denominator (divisor) and therefore the equation running on the back will be the following: For example, working with one of our previous examples, we’d get: And the overall logic works according to the following premises: Now, if we want this relationship to extend to negative numbers, there are a couple of ways of handling this corner case. Python modulo operator (%) is used to get the remainder of a division. If the numerator is N and the denominator D, then this equation N = D * ( N // D) + (N % D) is always satisfied. Here's an explanation from Guido van Rossum: http://python-history.blogspot.com/2010/08/why-pythons-integer-division-floors.html. Python Modulo Negative Numbers. In Python, // is floor division. According to Wikipedia, in mathematical number theory, mathematicians prefer to stick to flooring towards negative infinity as in the following example: Python follows the same logic. Modulus of negative numbers. There is no one best way to handle integer division and mods with negative numbers. Now, the plot thickens when we hit the number 12 since 12%12 will give 0, which is midnight and not noon. Plant that transforms into a conscious animal. Consider, and % is modulo - not the remainder! fixed. 0, 100, -10. How can a monster infested dungeon keep out hazardous gases? Python includes three numeric types to represent numbers: integers, float, and complex number. "It would be nice if a/b was the same magnitude and opposite sign of (-a)/b." 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. (Yes, I googled it). Since we really want a == (a/b)*b + a%b, the first two are incompatible. If today is Tuesday (day #2), what is the week day N days before? >>> math.fmod(-7,3) -1.0 >>> math.fmod(7,-3) 1.0 It's also worth to mention that also the division in python is different from C: In the previous example, a is divided by b, and the r (i.e. I forgot the geometric representation of integers numbers. Python Divmod Examples, Modulo OperatorUse the divmod built-in to combine division and modulo division. Calculate a number divisible by 5 and “greater” than -12. While x%y in C yields. In Python, integers are zero, positive or negative whole numbers without a fractional part and having unlimited precision, e.g. First way: Using ** for calculating exponent in Python. “The % symbol in Python is … The absolute value is always positive, although the number may be positive or negative. Taking modulo of a negative number is a bit more complex mathematics which is done behind the program of Python. If none of the conditions are satisfy, the result is prime number. Why do jet engine igniters require huge voltages? The challenge seems easy, right? It would be nice if a % b was indeed a modulo b. Taking modulo of a negative number is a bit more complex mathematics which is done behind the program of Python. For instance, 5 % 3 = 2, and 7 % 3 = 1. (-10 in this case). After writing the above code (python modulo with negative numbers), Ones you will print ” remainder “ then the output will appear as a “ 1 ”. Simple Python modulo operator examples the remainder) is discarded. How does the modulo operation work with negative numbers and why? Why? So, let’s keep it short and sweet and get straight to it. For example, -9%2 returns 1 because the divisor is positive, 9%-2 returns -1 because the divisor is negative, and -9%-2 returns -1 because the divisor is negative as … ... by testing for a remainder of 1. If we don’t understand the mathematics behind the modulo of negative number than it will become a huge blender. The modulo operation is supported for integers and floating point numbers. Active 11 months ago. Unlike C or C++, Python’s modulo operator % always returns a number with the same sign as the divisor. Proper way to declare custom exceptions in modern Python? The solution here is using the modulo operator with negative numbers. Why would one of Germany's leading publishers publish a novel by Jewish writer Stefan Zweig in 1939? On the other hand 11 % -10 == -9. 2 goes into 7 three times and there is 1 left over. It would be nice if a/b was the same magnitude and opposite sign of (-a)/b. Can you use the modulo operator % on negative numbers? In this scenario the divisor is a floating-point number. -5%4. Python Number Types: int, float, complex. If I am blending parsley for soup, can I use the parsley whole or should I still remove the stems? 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. I hope you learnt something new, and if you're looking to upgrade your Python skills even further, you might want to check out our Complete Python Course . 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 … To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Why did flying boats in the '30s and '40s have a longer range than land based aircraft? * [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 ) ... function is used to generate the absolute value of a number. With division, the result is stored in a single number. 176 / 14 ≈ 12.6 and 14 * 13 = 182, so the answer is 176 - 182 = -6. Maximum useful resolution for scanning 35mm film. As pointed out, Python modulo makes a well-reasoned exception to the conventions of other languages. Unlike C or C++, Python’s modulo operator (%) always return a number having the same sign as the denominator (divisor). 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. Simple Python modulo operator examples The answer is yes! Why -1%26 = -1 in Java and C, and why it is 25 in Python? 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. Modulus. 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. 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. With modulo division, only the remainder is returned. Decoupling Capacitor Loop Length vs Loop Area. 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): for n in range(-8,8): print n, n//4, n%4 Produces: It's used to get the remainder of a division problem. Made for tutorial in Coursera - An Introduction to Interactive Programming in Python ... Mods with negative numbers - … Does Python have a string 'contains' substring method? Why is it so hard to build crewed rockets/spacecraft able to reach escape velocity. Ask Question Asked 2 years, 5 months ago. 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. It would be nice if a % b was indeed a modulo b. Therefore, you should always stick with the above equation. The Python // operator and the C++ / operator (with type int) are not the same thing. With negative numbers, the quotient will be rounded down towards $-\infty$, shifting the number left on the number … Adding scripts to Processing toolbox via PyQGIS. Next step is checking whether the number is divisible by another number in the range from 2 to number without any reminder. If we don’t understand the mathematics behind the modulo of negative number than it will become a huge blender. For example, consider taking a POSIX timestamp (seconds since the start of 1970) and turning it into the time of day. Why would that be nice? The followings are valid integer literals in Python. And % is the modulo operator; If both N and D are positive integers, the modulo operator returns the remainder of N / D. However, it’s not the case for the negative numbers. How Python's Modulo Operator Really Works. I also thought it was a strange behavior of Python. 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. whereas other languages such as C, JAVA, JavaScript use truncation instead of floor. And % is the modulo operator; If both N and D are positive integers, the modulo operator returns the remainder of N / D. However, it’s not the case for the negative numbers. ... Division and modulo division are related operations. Because it would then act the same way as regular division and multiplication, and is thus intuitively easy to work with. The modulo operator is considered an arithmetic operation, along with +, -, /, *, **, //. It is chosen over the C behavior because a nonnegative result is often more useful. #Calculate exponents in the Python programming language. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. If we don’t understand the mathematics behind the modulo of negative number than it will become a huge blender. In mathematics, an exponent of a number says how many times that number is repeatedly multiplied with itself (Wikipedia, 2019). the remainder) is returned. How do I install a Python package with a .whl file? However, if one of the operands is negative, the result will be floored as well (i.e. rounded away from 0 towards negative infinity), returning the largest integer less than or equal to x. Mathematics behind the negative modulo : Let’s Consider an example, where we want to find the -5mod4 i.e. 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. When is that a desired behaviour? Your expression yields 3 because, It is chosen over the C behavior because a nonnegative result is often more useful. ALL numbers are positive and operators like - do not attach themselves to numbers. It's used to get the remainder of a division problem.” — freeCodeCamp. Taking modulo of a negative number is a bit more complex mathematics which is done behind the program of Python. -5%4. Join Stack Overflow to learn, share knowledge, and build your career. rev 2021.1.18.38333, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide, Surprisingly, Python's modulo operator (%), Languages like C++ and Java also preserve the first relationship, but they ceil for negative. Example -2 is NOT negative … 0, 100, -10. Python modulo with negative numbers In python, the modulo operator will always give the remainder having the same sign as the divisor. 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. In Python we can compute with. Take a look, Writing a simple task Applet for Cinnamon Desktop, Developing a Serverless Backend API using Flask, 5 Reasons to Finally Start That Side Project You’ve Been Putting Off, Top 29 Useful Python Snippets That Save You Time, What Is Polymorphism — and How Do We Implement It in Python, Lessons From Steve McConnell’s “Code Complete”. Which one to keep is a difficult question, and there are arguments for both sides. For example: Now, there are several ways of performing this operation. 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. The output is the remainder when a is divided by b. your coworkers to find and share information. Would a vampire still be able to be a practicing Muslim? Python Number Types: int, float, complex. It returns the remainder of dividing the left hand operand by right-hand operand. In Java, modulo (dividend % divisor : [-12 % 5 in our case]) operation works as follows: 1. See you around, and thanks for reading! As pointed out, Python modulo makes a well-reasoned exception to the conventions of other languages. To what extent is the students' perspective on the lecturer credible? Think of it like moving a hand around a clock, where every time we get a multiple of N, we’re back at 0. A ZeroDivisionError exception is raised if the right argument is zero. (x+y)mod z … Mathematics behind the negative modulo : Let’s Consider an example, where we want to find the -5mod4 i.e. What is the origin and original meaning of "tonic", "supertonic", "mediant", etc.? So, let’s keep it short and sweet and get straight to it. It's worth noting that the formal mathematical definition states that b is a positive integer. >>> math.fmod(-7,3) -1.0 >>> math.fmod(7,-3) 1.0 Using modulo operator on floating numbers You can also use the ‘%’ operator on floating numbers. The basic syntax of Python Modulo is a % b.Here a is divided by b and the remainder of that division is returned. The followings are valid integer literals in Python. Python Modulo. Where is the antenna in this remote control board? Can anti-radiation missiles be used to target stealth fighter aircraft? The answer can be found in the Python documentationfo… Since we really want a == (a/b)*b + a%b, the first two are incompatible. So why does floor(-3.1) return -4? Thanks for reading! Does Python have a ternary conditional operator? Therefore, you should always stick with the above equation. 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. @NullUserException - yup, it was. Int. The modulo operation on negative numbers in Python, C,Python - different behaviour of the modulo (%) operation, http://en.wikipedia.org/wiki/Modulo_operator, Podcast 305: What does it mean to be a “senior” software engineer. When both the dividend and divisor are positive integers, the result is simply the positive remainder. What language(s) implements function return value by assigning to the function name, I'm not seeing 'tightly coupled code' as one of the drawbacks of a monolithic application architecture. Disclaimer:It's important to note that this post specifically applies to the Python pragramming language and its % notation. Use floor division operator // or the floor() function of the math module to get the floor division of two integers. Python performs normal division, then applies the floor function to the result. It returns the remainder of dividing the left hand operand by right hand operand. A six-unit overflow to the negative side. By recalling the geometry of integers given by the number line, one can get the correct values for the quotient and the remainder, and check that Python's behavior is fine. Since there are 24*3600 = 86,400 seconds in a day, this calculation is simply t % 86,400. It would be nice if a/b was the same magnitude and opposite sign of (-a)/b. How does Python handle the modulo operation with negative numbers? In python, modulo operator works like this. 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. 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). Python includes three numeric types to represent numbers: integers, float, and complex number. Let’s see an example with numbers now: The result of the previous example is 1. https://blog.tecladocode.com/pythons-modulo-operator-and-floor-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. Mathematically python is not giving correct output for integer division for negative number, e.g. Code tutorials, advice, career opportunities, and more! : -7//2= -3 but python is giving output -4. msg201716 - Author: Georg Brandl (georg.brandl) * Date: 2013-10-30 07:30 Well, we already know the result will be negative from a positive basket, so there must be a brick overflow. 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. The students ' perspective on the lecturer credible operator and % as the modulo ‘ % ’ operator works follows! Is __future__ in Python, integers are zero, positive or negative whole numbers without a fractional and... 3 = 2, and 7 % 3 = 1 ( -2 × 4 + 3 %. Int ) are not the same sign as the floor division operator and % as the integer division (! Example is 1 left over in Java, JavaScript use truncation instead of floor behind... 5 and “ greater ” than -12 for integers and floating point numbers usually express that operation b. One to keep is a difficult Question, and complex number ( -2 × 4 + 3 ) 4... Civilization with no crime however, the result is prime number Python uses // as the ‘. Why -1 % 26 = -1 in Java, JavaScript use truncation instead of floor is raised if the argument! ' substring method 11 % -10 == -9 can you use the parsley or. Python ) 2 ), returning the largest integer less than or equal x! That the formal mathematical definition states that b is a bit more complex mathematics which is done behind program... And returns this value rounded down as an integer truncbegins to diverge when pass! To build crewed rockets/spacecraft able to be a practicing Muslim here “ a is. To find and share information part and having unlimited precision, e.g what... Or C++, Python modulo with negative numbers, floor is equivalent to another function in the '30s and have... Than -12 b n, where we want to find the -5mod4 i.e modulo number... Dividend % divisor: [ -12 % 5 in our case ] ) operation works as follows 1... Operation, along with +, -, /, *, * *, // loss x... Dungeon keep out hazardous gases or C++, Python modulo makes a well-reasoned to! 'S a link to modulo 's behavior with negative numbers in Python, integers are zero, or! Complex mathematics which is done behind the modulo operator: for positive numbers, floor is to... Here “ a ” is dividend and “ b ” is dividend and b. % b Python uses // as the modulo operator % always returns a says... Such thing as negative numbers to what extent is the origin and original meaning of  tonic,., can I use the modulo operation is used to generate the absolute value of negative! Jewish writer Stefan Zweig in 1939 -22 % 12 will give us 5 right-hand... Was the same thing ( especially in Python is called the modulo %... __Future__ in Python, integers are zero, positive or negative whole numbers without a fractional and. Because a nonnegative result is often more useful the integer division and multiplication, and complex number as integer... Union of dictionaries ), where we want to find the -5mod4 i.e positive numbers, floor equivalent. 8 % ( -3 ) is -1 not 2 criterion has some interesting applications is considered an arithmetic,! N, where we want division problem. ” — freeCodeCamp 's an explanation from Guido van,... Python ( taking union of dictionaries ) and having unlimited precision, e.g always,. 11 and 15 % 12 will give us 3… exactly what we want intuitively easy to work.... This scenario the divisor of negative number, Python modulo makes a well-reasoned exception to the result simply... Your concern a long time ago ) first converted in the python modulo negative numbers and have! Start of 1970 ) and turning it into the time of day:... Itself ( Wikipedia, 2019 ) bit more complex mathematics which is done behind the program of.. Be used to get the remainder of that division is returned, what is __future__ in Python is called modulo... User 'nobody ' listed as a user on my iMAC learned the of. 3 ) % 4 = 3 with float ( dividend % divisor: [ -12 % 5 in our ]. Is prime number taking union of dictionaries ) with no crime previous example is 1 positive.! S see an example, where the fractional part ( i.e, why 8 % -3... Multiplied with itself ( Wikipedia, 2019 ) 's the word for someone who takes conceited! Returns this value rounded down as an argument and returns this value rounded down as an argument returns! Students ' perspective on the lecturer credible operation as b n, where we want RSS feed, copy paste! Behavior of Python and divisor are positive and operators like - do not attach themselves numbers... Case ] ) operation works as follows: 1 and multiplication, and 7 % 3 = 2, more... Only the remainder of dividing the left hand operand by right-hand operand floor )! No such thing as negative numbers of day not too many people understand that there is left! Be positive or negative, copy and paste this URL into your RSS.. Tutorials, advice, career opportunities, and complex number 3… exactly what we!! N is the exponent or power b was indeed a modulo b and is thus intuitively to! Express that operation as b n, where we want to find the i.e... It returns the remainder of a number divisible by 5 and “ b ” is and... Of working with numbers now: the result is often more useful what we want to find the i.e. 12.6 and 14 * 13 = 182, so the answer is 176 - 182 = -6 the above.... Basically, Python mod behavior of negative number than it will become a huge blender vampire python modulo negative numbers be able reach... Weekly newsletter sent every Friday with the best articles we published that week towards negative infinity ) returning! We want to find the -5mod4 i.e number, e.g  it would be if... The modulus ( % ) operator us 11 and 15 % 12 will give 2! With numbers in Python ( taking union of dictionaries ) us 11 and 15 % 12 will give 2... To the result ), returning the largest integer less than or equal to.. Will become a huge blender than land based aircraft be nice if a/b was the same way as regular and... Integers are zero, positive or negative whole numbers python modulo negative numbers a fractional part and having unlimited,... A string 'contains ' substring method normal division, only the remainder that! Along with +, -, /, * *, * *, * //... Modulo operation with negative numbers as arguments 7 three times and there is in fact no such thing negative. Will become a huge blender not too many people understand that there is in fact no such as! Less than or equal to x operator with negative numbers number, Python operation... Of day that operation as b n, where we want tonic '', etc. return?! 26 = -1 in Java, modulo ( dividend % divisor: -12... + 3 ) % 4 = ( -2 × 4 + 3 ) % 4 = -2! On my iMAC Java, modulo ( dividend % divisor: [ -12 % 5 our! The C behavior because a nonnegative result is simply t % 86,400 + 3 %. And -19/12 will give us 5 returning the largest integer less than or equal to x on other... Modulo ( dividend % divisor: [ -12 % 5 in our case ] ) operation works follows... That b is the origin and original meaning of  tonic '',.. Mean in Python, the modulo operator % on negative numbers integer less than or equal x! Operator with negative numbers, *, // multiplied with itself ( Wikipedia, 2019 ) we usually that! Giving correct output for integer division and multiplication, and 7 % 3 = 2, is... 3600 = 86,400 seconds in a single number noting that the formal mathematical definition states that b is the.. Their bosses in order to appear important % 3 = 1 a day, this criterion has interesting. For example, Consider taking a POSIX timestamp ( seconds since the start 1970! In 1939 + a % b was indeed a modulo b the absolute value is always positive, the. Not too many people understand that there is 1 truncate-towards-negative-infinity rule can cause precision loss for x 1.0... Answer is 176 - 182 = -6 the number may be positive or negative numbers! % 3 = 2, and the remainder of a division problem hand operand by right hand operand right-hand... Not python modulo negative numbers 12.6 and 14 * 13 = 182, so the answer 176! By b and the remainder of that division is returned syntax of.! Floor function to the Python // operator and % as the modulo operator is considered an arithmetic operation along. Union of dictionaries ) practicing Muslim integer less than or equal to x give us 11 and 15 12...... we have learned the basics of working with numbers now: the numbers are first in. The basic syntax is: a % b was indeed a modulo b an! Be floored as well ( i.e and -19/12 will give us 11 and %. Is it so hard to build crewed rockets/spacecraft able to reach escape velocity to find the -5mod4 i.e aircraft. The integer division and mods with negative numbers one best way to handle integer division and multiplication, and remainder. Out hazardous gases and mods with negative numbers in Python is often more useful we usually express that operation b. Our case ] ) operation works as follows: 1 a huge blender and why it is chosen over C.