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3 | 3 | After learning how to use other people's functions, it's time to write our own! We will look at the anatomy of how a function is constructed, and see bunch of examples in action. |
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5 | | -{width="300"} |
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7 | 5 | First, we remind ourselves why we write functions in the first place. We write functions for two main, often overlapping, reasons: |
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9 | 7 | 1. Following DRY (Don't Repeat Yourself) principle: If you find yourself repeating similar patterns of code, you should write a function that executes that pattern. This saves time and the risk of mistakes. |
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61 | 59 | Within a function, all input arguments and any new variables defined are stored in a "**local environment**", and is only accessible within the function's body. The overall environment of the program is called the "**global environment**" and can be also accessed within the function. |
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63 | | -The reason of having some of this "privacy" in the local environment is to make functions modular - they are independent little tools that should not interact with the rest of the global environment. Imagine someone writing a tool that they want to give someone else to use, but the tool depends on your environment, vice versa. |
| 61 | +The reason of having some of this "privacy" in the local environment is to make functions modular - they are independent little tools that should not interact with the rest of the global environment. Imagine you writing a function that you want to give someone else to use, but your function depends on your global environment - it would not be portable! |
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65 | | -To illustrate the distinguish between a the local and global environment, the following tool allows you to step through Python code execution line-by-line and see the relationship between order of execution, variables, and environments. The "Global frame" refers to the global environment, and "add_numbers" refer to the local environment for the function `add_numbers()`. |
| 63 | +To illustrate the distinction between a the local and global environment, the following tool allows you to step through Python code execution line-by-line and see the relationship between order of execution, variables, and environments. The "Global frame" refers to the global environment, and "add_numbers" refer to the local environment for the function `add_numbers()`. |
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67 | 65 | <iframe width="800" height="500" frameborder="0" src="https://pythontutor.com/iframe-embed.html#code=def%20add_numbers%28num1,%20num2%29%3A%0A%20%20%22%22%22%20Adds%20two%20input%20numbers%20together.%20%22%22%22%0A%20%20result%20%3D%20num1%20%2B%20num2%0A%20%20return%20result%0A%20%20%0Aadd_numbers%283,%204%29&codeDivHeight=400&codeDivWidth=350&cumulative=false&curInstr=0&heapPrimitives=nevernest&origin=opt-frontend.js&py=311&rawInputLstJSON=%5B%5D&textReferences=false"> |
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112 | 110 | ## Exercises |
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114 | | -Exercise for week 3 can be found [here](https://colab.research.google.com/drive/1d07xM-0vCFNVFoJF32yBMvNtUsGjC_n3?usp=sharing). |
| 112 | +Exercise for week 4 can be found [here](https://colab.research.google.com/drive/1d07xM-0vCFNVFoJF32yBMvNtUsGjC_n3?usp=sharing). |
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