Gain insights into Pythonic programming techniques. Learn about documentation, data types, safety, performance, and function design to write fast, maintainable, and correct Python code.

python3.8.tar.gz

Python3.8

Python3.8Code

This course is an invaluable resource for anyone who wants to learn the correct Pythonian way of writing highly performant code that is easy to maintain and grow.

The course is divided into six chapters: documentation tips, data types/data structures tips, safety tips, performance tips, function design tips, and general tips. Throughout each chapter, you will get hands-on experience working with real Python code to help ingrain each concept.

By the end, you will know how to make your programs correct, safe, fast, and easy to maintain.

Pythonic Programming Tips for Software Engineers

## Compare one to many
We have a variable and we want to check if its value is permissible. Let’s say that the user enters the name of a day and we want to check if it's Saturday or Sunday. It seems obvious in Python, but it's not:
```python
if day.lower() == 'saturday' or 'sunday': # It’s weekend!
```

The boolean `or` operator has lower precedence than the comparison operator (`==`), which means that the comparison is evaluated before the boolean operator. So if we place parentheses around the higher-precedence operator to avoid confusion, the above statement looks like this:
```python
if (day.lower() == 'saturday') or 'sunday': ...
```

The value of an `or` expression is true if any of its operands are true. The non-empty `'sunday'` string is always interpreted as true. Thus, the condition is always true, regardless of the day. It's good to have a never-ending weekend.

Perhaps, then, we should adjust the precedence by enclosing the `or` expression in the parentheses?
```python
if day.lower() == ('saturday' or 'sunday'): ...
```

No, again. The value of the `or` operator is first `True` operand, or `False` if both operands are false. Because `'saturday'` is a non-empty string, it's interpreted as true. The expression in the parentheses is always `'saturday'` and never `'sunday'`. The expression treats Sunday as a weekday. We’d rather have a never-ending weekend than a one-day weekend.

The correct way to go is to check if the day is in a collection of suitable days using the membership operator, `in`. The collection can be a list, a tuple, or even a dictionary, but we get optimal performance by using sets.

# Compare one to many
We have a variable and we want to check if its value is permissible. Let’s say that the user enters the name of a day and we want to check if it's Saturday or Sunday. It seems obvious in Python, but it's not:
```python
if day.lower() == 'saturday' or 'sunday': # It’s weekend!
```

The boolean `or` operator has lower precedence than the comparison operator (`==`), which means that the comparison is evaluated before the boolean operator. So if we place parentheses around the higher-precedence operator to avoid confusion, the above statement looks like this:
```python
if (day.lower() == 'saturday') or 'sunday': ...
```

The value of an `or` expression is true if any of its operands are true. The non-empty `'sunday'` string is always interpreted as true. Thus, the condition is always true, regardless of the day. It's good to have a never-ending weekend.

Perhaps, then, we should adjust the precedence by enclosing the `or` expression in the parentheses?
```python
if day.lower() == ('saturday' or 'sunday'): ...
```

No, again. The value of the `or` operator is first `True` operand, or `False` if both operands are false. Because `'saturday'` is a non-empty string, it's interpreted as true. The expression in the parentheses is always `'saturday'` and never `'sunday'`. The expression treats Sunday as a weekday. We’d rather have a never-ending weekend than a one-day weekend.

The correct way to go is to check if the day is in a collection of suitable days using the membership operator, `in`. The collection can be a list, a tuple, or even a dictionary, but we get optimal performance by using sets.

Learn how conditions work in Python in different ways.

Introduction

Documentation Tips

General Tips

Data Types and Data Structures Tips

Function Tips

Performance Tips

Safety Tips

Wrapping Up

Conditions Related Tips

Compare one to many