Question I would like to understand the basics of how to write and execute a python program on Linux OS. Can you explain it with a simple example Answer. How To Use Break, Continue, and Pass Statements when Working with Loops in Python 3. If Statements Hands on Python Tutorial for Python 3. Simple ConditionsThe statements introduced in this chapter will involve tests or. More syntax for conditions will be introduced later. Python. Try each line separately in the. Python 3 Example Program' title='Python 3 Example Program' />Shell. TrueYou see that conditions are either True or False with no. These are the only possible Boolean values named after. George Boole. In Python the name. Boolean is shortened to the type bool. It is the type of the. Simple if StatementsRun this example program, suitcase. Try it at least twice, with. As you an see, you get an extra result. The main code is weightfloatinputHow many pounds does your suitcase weigh There is a 2. Thank you for your business. The middle two line are an if statement. It reads pretty much. English. If it is true that the weight is greater than 5. WritingHack3.png' alt='Python 3 Example Program' title='Python 3 Example Program' />If it is not true. In any event, when. In this case that is the statement. Thank you. The general Python syntax for a simple if statement isifcondition indented. Statement. Block. If the condition is true, then do the indented statements. If the. condition is not true, then skip the indented statements. Another fragment as an example ifbalancelt 0 transfer balance transfer enough from the backup account backup. Accountbackup. Account transferbalancebalancetransfer. As with other kinds of statements with a heading and an indented. The assumption. in the example above is that if an account goes negative, it is. In the examples above the choice is between doing something if the. True or nothing if the condition is False. Often there is a choice of two possibilities, only one of which. StatementsRun the example program, clothes. Try it at least twice, with. As you can see, you get different results. The main code of clothes. What is the temperature Wear shorts. Wear long pants. printGet some exercise outside. The middle four lines are an if else statement. Again it is. close to English, though you might say otherwise instead of. There are two indented blocks. One, like in the simple if statement, comes right after the. In the if else form this is followed by an. In an if else. statement exactly one of two possible indented blocks is executed. A line is also shown outdented next, about getting exercise. Since it is outdented, it is not a part of the if else statement. It is always executed in the normal forward flow of statements. The general Python if else syntax isifcondition indented. Statement. Block. For. True. Conditionelse indented. Statement. Block. For. False. Condition. These statement blocks can have any number of statements, and can. See Graduate Exercise. More Conditional ExpressionsAll the usual arithmetic comparisons may be made, but many do not. Meaning. Math Symbol. Python Symbols. Less thanlt lt Greater than Less than or equallt Greater than or equal EqualsNot equalThere should not be space between the two symbol Python. Notice that the obvious choice for equals, a single equal sign. An annoying second equal sign. This is because the single equal sign is already used. Python, so it is not available for tests. Warning. It is a common error to use only one equal sign when you mean to test. Tests for equality do not make an assignment, and they do not. Any expressions can be tested for. They do not need to be numbers Predict the results and try each line in the Shell x5xx5x6xx6x6. HIhi1,22,1An equality check does not make an assignment. Strings are case. Order matters in a list. Try in the Shell When the comparison does not make sense, an Exception is caused. Following up on the discussion of the inexactness of float. String Formats for Float Precision, confirm that Python. Write a simple. condition into the Shell to test. Here is another example Pay with Overtime. Given a persons work. Hours worked over 4. This is a natural. Read the setup for the function defcalc. Weekly. Wagestotal. Hours,hourly. Wage Return the total weekly wages for a worker working total. Hours, with a given regular hourly. Wage. Include overtime for hours over 4. The problem clearly indicates two cases when no more than 4. In case. more than 4. Hours. You are encouraged to think about a. You can try running my complete example program, wages. The format operation at the end of the main function. String Formats for Float Precision to. Weekly. Wagestotal. Hours,hourly. Wage Return the total weekly wages for a worker working total. Hours, with a given regular hourly. Wage. Include overtime for hours over 4. Hourslt 4. 0 total. Wageshourly. Wagetotal. Hourselse overtimetotal. Hours 4. 0total. Wageshourly. Wage. Wagevertimereturntotal. Wagesdefmain hoursfloatinputEnter hours worked wagefloatinputEnter dollars paid per hour totalcalc. Weekly. Wageshours,wageprintWages for hours hours at wage. Here the input was intended to be numeric, but it could be decimal. Below is an equivalent alternative version of the body of. Weekly. Wages, used in wages. It uses just one. There are generally a number of ways you might. Hourslt 4. 0 regular. Hourstotal. Hoursovertime0else overtimetotal. Hours 4. 0regular. Hours4. 0returnhourly. Wageegular. Hours1. Wagevertime. 3. Graduate ExerciseWrite a program, graduate. Print whether of not they have enough. At Loyola University Chicago 1. Head or Tails ExerciseWrite a program headstails. It should include a function flip. It randomly prints either. Heads or Tails. Accomplish this by choosing 0 or 1 arbitrarily with random. Heads. when the result is 0, and Tails otherwise. In your main program have a simple repeat loop that calls flip. Heads and. Tails. Strange Function ExerciseSave the example program jump. Func. Stub. py as jump. Func. py. and complete the definitions of functions jump and main as. In the jump function definition use an if else. In the main function definition. The jump function is introduced for use in. Strange Sequence Exercise, and others after that. Multiple Tests and if elif StatementsOften you want to distinguish between more than two distinct cases. True or False. so the only direct choice is between two options. As anyone who has. Questions knows, you can distinguish more cases by. If there are more than two choices, a single. Since most any kind. For instance consider a. A, B. C, D or F, where the cutoffs for A, B, C, and D are. One way to write the function. Gradescore ifscore 9. Aelse grade must be B, C, D or Fifscore 8. Belse grade must be C, D or Fifscore 7. Celse grade must D or Fifscore 6. Delse letterFreturnletter. This repeatedly increasing indentation with an if statement as. A preferred. alternative in this situation, that avoids all this indentation, is. Gradescore ifscore 9. Aelifscore 8. Belifscore 7. Celifscore 6. Delse letterFreturnletter. The most elaborate syntax for an. Statement. Block. For. True. Condition. Statement. Block. For. First. True. Condition. 2elifcondition. Statement. Block. For. First. True. Condition. 3elifcondition. Statement. Block. For. First. True. Condition. 4else indented. Statement. Block. For. Each. Condition. False. The if, each elif, and the final else line are all. There can be any number of elif lines, each followed. Three happen to be illustrated above. With. It is the one corresponding to the first. True. condition, or, if all conditions are False, it is the block. SWIG and Python. Caution This chapter is under repair This chapter describes SWIGs support of Python. SWIG is compatible. Python versions including Python 3. Python 2. 6. as well as older versions dating back to Python 2. For the best results. Python 2. 3 or newer. This chapter covers most SWIG features, but certain low level details. At the. very least, make sure you read the SWIG. Basics chapter. To build Python extension modules, SWIG uses a layered approach in which. C and other parts are. Python. The C layer contains low level wrappers whereas Python code. This layered approach recognizes the fact that certain aspects of. C or C. Furthermore, by generating code in both. In describing the Python interface, this chapter starts by covering the. Python modules. Next, the Python interface to common C and C programming features is. Advanced customization features such as typemaps are then. Preliminaries. 31. Running SWIG. Suppose that you defined a SWIG module such as the following. File example. i. SWIGFILEWITHINIT. The define SWIGFILEWITHINIT line inserts a macro that specifies that the. C file should be built as a python extension, inserting the module. This. i file wraps the following simple C file. File example. c. This should probably return an error, but this is simpler. With the header file. File example. h. To build a Python module, run SWIG using the python option. If building a C extension, add the c option. This creates two different files a CC source file examplewrap. Python source file example. The generated C. source file contains the low level wrappers that need to be compiled and linked with the. CC application to create an extension module. The Python source file. This is the file that you will import to use the module. The name of the wrapper file is derived from the name of the input file. For example, if the. To change this, you can use the o option. The name of the Python file is derived. If the module name is example. The following sections have further practical examples and details on. Using distutils. The preferred approach to building an extension module for python is to compile it with. Distutils Docs. Distutils takes care of making sure that your extension is built with all the correct. Python it is run with. Distutils will compile your. DLL. so on Linux,. Windows, etc. In addition, distutils can handle installing your package into. A configuration file conventionally called setup. The distutils will. Here is a sample setup. SWIG example. from distutils. Extension. examplemodule Extensionexample. SWIG Docs. description Simple swig example from docs. In this example, the line examplemodule Extension. Extension. The swig and other python extension modules tradition is for the compiled. If the name. of your python module is example. The setup call then sets up distutils to build your package, defining. Once this is saved as setup. And a. so, or. pyd or. It will build a version that matches the. Taking apart the command line. Otherwise, it will put it inside a build hierarchy, and youd have to move it to use it. The distutils have many other features, consult the python distutils docs for details. This same approach works on all platforms if the appropriate compiler is installed. Windows Python using Ming. GW. 3. 1. 2. 3 Hand compiling a dynamic module. While the preferred approach to building an extension module is to use the distutils, some. To do this, you need to compile your. Linux. swig python example. O2 f. PIC c example. O2 f. PIC c examplewrap. Iusrlocalincludepython. The exact commands for doing this vary from platform to platform. However, SWIG tries to guess the right options when it is installed. Therefore. you may want to start with one of the examples in the SWIGExamplespython. If that doesnt work, you will need to read the man pages for. You might also. check the SWIG Wiki for. When linking the module, the name of the output file has to match the name. If the name of your module is example, then the. The name of the module is specified using the module directive or the. Compatibility Note In SWIG 1. This is because modules. C only extensions without the extra Python. Python code was supported as an optional. This has been changed in SWIG 1. Python extension modules. For example, the socket. Many other built in Python modules follow a similar convention. Static linking. An alternative approach to dynamic linking is to rebuild the Python. In the past. this approach was sometimes necessary due to limitations in dynamic loading. However, the situation has improved greatly. The usual procedure for adding a new module to Python involves finding. Python source, adding an entry to the ModulesSetup file. Python Makefile. However. Python versions have changed the build process. You may need to edit. Python distribution instead. In earlier versions of SWIG, the embed. For example. module example. Myvariable. include embed. Include code for a static version of Python. The embed. i library file includes supporting code that. Python. To rebuild the interpreter. Xlinker export dynamic. DHAVECONFIGH Iusrlocalincludepython. Iusrlocallibpython. Lusrlocallibpython. You will need to supply the same libraries that were used to build Python the first. This may include system libraries such as lsocket, lnsl. Assuming this actually works, the new version of Python. Comment In practice, you should probably try to avoid static. Some programmers may be inclined. However, the performance gained by static linking tends to be rather. Compatibility note The embed. Even though it. appears to work with Python 2. If using static linking, you might want to rely on a different approach. Using your module. To use your module, simply use the Python import statement. If. all goes well, you will be able to this. A common error received by first time users is the following. Traceback most recent call last. File lt stdin, line 1, in File example. Import. Error No module named example. If you get this message, it means that you either forgot to compile the wrapper. Make sure that you compiled the wrappers into a module called example. And. dont forget the leading underscore. Another possible error is the following. Traceback most recent call last. File lt stdin, line 1, in Import. Error dynamic module does not define init function initexample. This error is almost always caused when a bad name is given to the shared object file. For example, if you created a file example. Alternatively, this error could arise if the name of the module is. Double check the interface to make sure the module name and the shared object. Another possible cause of this error is forgetting to link the SWIG generated. Another common error is something similar to the following. Traceback most recent call last. File example. py, line 3, in Import. Error. example. This error usually indicates that you forgot to include some object. Make. sure you compile both the SWIG wrapper file and your original program. Make sure you pass all of the required libraries. Sometimes unresolved symbols occur because a wrapper has been created. This usually. occurs when a header file includes a declaration for a function that. To fix this, you can either edit. SWIG input file to remove the offending declaration or you can use. Joomla Job Portal Templates on this page. Finally, suppose that your extension module is linked with another library like this.