Python Crash Course
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# Complex Comparisons

In the last article we looked at very basic example of `if` `else` and `elif` statements. However things can get a little more complex than that depending on your program's functionality.

‍Let's have a closer look to start this off.

Let's introduce something called Reynold's number Re. When studying the flow of some fluid inside of a pipe:

• ‍If Re is between 2000 and 10000, then the flow is transitional
• If Re is smaller than 2000, then the flow is laminar
• If Re if bigger than 10000, then the flow is turbulent

‍let's execute some code that demonstrates if the flow is transitional or not:

## Using multiple comparison operators

``````reynolds_number = 5000

if 2000 < reynolds_number < 10000﻿:
print﻿(﻿"The flow is transitional"﻿)``````

`‍>> The flow is transitional`

The code above checks if Re is between `2000` and `10000`. You can use multiple comparison operators in the same statement to do so.

## Using logical operators

The example above can also be done using logical operators:

``````reynolds_number = 5000

if reynolds_number > 2000 and reynolds_number < 10000﻿:
print﻿(﻿"The flow is transitional"﻿)``````

`‍>> The flow is transitional‍`

The code above renders the same result as the last example. However, this time we use the logical operator `and` to determine the condition. We checked if Re is bigger than `>` `2000` `and` if Re is smaller than `<` `10000`.

‍change Re to `11000`. Now if you run the code, nothing should be executed, since `and` requires both conditions to be true. and Re is not smaller than `10000`.

Let's also use the `or` operator to determine if the flow is not transitional:

``````reynolds_number = 1000

if reynolds_number <= 2000 or reynolds_number >= 10000﻿:
print﻿(﻿"The flow is not transitional"﻿)``````

`>‍> print("The flow is not transitional")`

The above code checks if Re is smaller or equal than `<=` `2000` `or` if Re is bigger or equal than `>=` `10000`. We chose a Re, which satisfies the first condition. Since `or` only requires one of the conditions to be True. The code below it will execute.

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