This technique is mainly used to determine the complexity of a piece of code or functionality. Is cyclomatic complexity density a good software quality. Pymetrics optionally outputs stdout, sql command files and csv. If the complexity of a method, function or property exceeds a configurable threshold, the method, function or property is marked with a warning highlight squiggly. Pdf django web framework software metrics measurement. Pylint contains checkers for pep8 code style compliance, design, exceptions and many other source code analysis tools. Cyclomatic complexity metric practices for python stack. Studies show a correlation between a programs cyclomatic complexity and its maintainability and testability, implying that with files of higher complexity there is a higher probability of errors when fixing, enhancing, or refactoring source code. Python isnt special when it comes to cyclomatic complexity.
Refactoring python applications for simplicity real python. Pyflakes parses source files for errors and reports on them. An extensible cyclomatic complexity analyzer for many programming languages including. Complexity also might take in to account nesting of loops, etc. Cyclomatic complexity approximates the number of paths that can be taken during the execution of a function and hence, the minimum number of tests cases necessary to test it thoroughly. Cyclomatic complexity really is just a scary buzzword.
Cyclomatic complexity density cyclomatic complexity lines of code i was reading previous discussions about cyclomatic complexity and there seems to be a sort of consensus that it has mixed usefulness, and as such there probably isnt a strong motive for using it over a simple lines of code loc metric. Cyclomatic complexity is a source code complexity measurement that is being correlated to a number of coding errors. Cyclomatic complexity is a metric for the measurement of complexity of a software. Radon is a python library that computes a couple of code metrics, one of which is code complexity. Cyclomatic complexity is merely a guide to complexity, and you are using it poorly if you change this function based on it. I am handling a big project where i am supposed to reduced the cc for methods that have cc 10. The algorithm was developed by thomas mccabe back in the 1970s. Straightline code has zero cyclomatic complexity, while. I used the argon library to calculate the cyclomatic complexity of the argon library written in python. It is calculated by developing a control flow graph of the code that measures the number of linearlyindependent paths through a program module. Specifically, difficulty of testing grows proportionately with cyclomatic complexity. Experience shows that when the branching is high, that code is harder to understand and change reliably than code in which the branching is lower. The technique was developed by macabe and helps to identify the below 3 questions for the programsfeatures. N represents a number of nodes in the control flow graph.
Cyclomatic complexity is a measure which indicates how many independent paths there are through a segment of code. Based on the cyclomatic complexity measure of mccabe, structured testing uses the control flow structure of software to establish path coverage criteria. P represents a number of nodes that have exit points in the control flow graph. The selected threshold is based on categories established by the software. This script borrows heavily from gary bernhardts vim plugin pycomplexity, but the python code that takes care of the analysis has been rewritten to use radon. Cc really measures the amount of branching in a suite of code. To calculate complexity we use the cc command line argument and specify the directories or files we want to compute statistics on. Is there is a free software tool to measure the complexity of software by using mccabe and halstead metrics. In fact its a measure of code complexity used in software development to point out more complex parts of code more likely to be buggy, and therefore has to be very carefully and thoroughly tested.
What is cyclomatic complexity learn with an example. For years now, ive gone with the assumption that 10 was the limit. Radon is a tool for obtaining raw metrics on line counts, cyclomatic complexity, halstead metrics and maintainability metrics. The code is analyzed and a complexity number is determined. If nothing happens, download github desktop and try again. Cyclomatic complexity software engineering stack exchange. After discovering the number of independent paths through the code by computing the cyclomatic complexity, you next design test cases to execute each of these paths. Is there is a free software tool to measure the complexity. Cyclomatic complexity is a software metric used to indicate the complexity of a program. Keeping track of python code metrics sourcecontribute. Cyclomatic complexity cc is the measure of linearly independent paths through a program. Many authors criticized cyclomatic complexity in many. Cyclomatic complexity will be high for methods with a high number of decision statements including ifwhilefor statements.
Cqse blog mccabes cyclomatic complexity and why we don. After all, almost every existing software quality tool calculates this metric and so it is very well known. Lower the programs cyclomatic complexity, lower the risk to modify and easier to. Travisci badge coveralls badge pypi latest version badge pypi downloads badge download. In this series of articles we have been discussing methods that can be applied to reduce cyclomatic complexity of code. It is a quantitative measure of the number of linearly independent paths through a programs source code. Mccabes cyclomatic complexity and why we dont use it. As complexity has calculated as 3, three test cases are necessary to the complete path coverage for the above example. Contribute to pycqamccabe development by creating an account on github. It counts the nloc lines of code without comments, ccn cyclomatic complexity number. Cc measures how much branching logic is in a chunk of code. To calculate complexity we use the cc command line. Cyclomatic complexity with example software testing class. It is a software metric used to indicate the complexity of a program.
The following steps should be followed for computing cyclomatic complexity and test cases design. A vim plugin to show cyclomatic complexity of python code. It is computed using the control flow graph of the program. Certainly cyclomatic complexity isnt the only measurement, but it can help. If a method has cyclomatic complexity of 25, this means that you would need to write 25 tests or at least invoke the method 25 times before you addressed each. It will emit a warning if the mccabe complexity of a. Cyclomatic complexity is a very common buzz word in the development community. Just download the files into any directory on your system. Complexity is determine by branching if statements, etc. Measuring cyclomatic complexity of python code david. Cyclomatic complexity plugin for resharper this is a resharper plugin that measures cyclomatic complexity as you type. Cyclomatic complexity with example the cyclomatic complexity metric is based on the number of decisions in a program. Radon cyclomatic complexity result the third measurement is to know django maintainability index mi, by issuing a command. Im analyzing a solution, and im trying to make a determination of the quality of the code.
Cyclomatic complexity for python code gary wilson jr. For python, you can install these tools with the following line. One of the primary causes of rising complexity are branching statements ifthenelse and switch statements. Cyclomatic complexity of functions python queries semmle. This metric although widely cited has many limitations.
This was a cloud computing task given in the module internet applications. Cyclomatic complexity of a code section is the quantitative measure of the number of linearly independent paths in it. Cyclomatic complexity is a measure of a modules structural complexity. Cyclomatic complexity is a way to determine if your code needs to be refactored. Lizard is a free open source tool that analyse the complexity of your source code right away supporting many programming languages, without any extra setup. E represents a number of edges in the control flow graph. Its ok to build very complex software, but you dont have to build it in a complicated way. Python ruby ttcn3 by default lizard will search for any source code that it knows an mix all the result together.
The nodes in the graph indicate the smallest group of commands of a program, and a directed edge. Finding cyclomatic complexity of repo using multiple nodes. Mccabe cyclomatic complexity rogue wave documentation. Rerunning with the above example will now look better. Users can also define their own metrics using data from pymetrics. Lets understand cyclomatic complexity with the help of the below example. Radon is a python tool which computes various code metrics.
1546 834 1231 962 579 1124 293 1452 822 1066 719 336 1438 1242 197 92 1089 751 507 1654 573 583 213 560 672 1117 776 498 206 1205 90 1262 279 408