# 5 Best Ways to Program a Bulb Switcher Using a Binary String in Python

Rate this post

π‘ Problem Formulation: Imagine you have a row of bulbs, each can be either off (0) or on (1). A bulb switcher program receives a binary string representing the current state of the bulbs and decides which bulb to toggle to reach a desired lighting pattern. This article will explore five Python methods for creating such a program, with an example input of `'10101'` and an example target output of `'11111'`.

## Method 1: Iterative Approach

This method involves iterating over each bulb represented in the binary string. The program will check the current state and toggle it if necessary to match the target state. The function specificity lies in changing the string into a list for easy manipulation.

Here’s an example:

```def switch_bulbs(current_state, target_state):
bulbs = list(current_state)
for i in range(len(bulbs)):
if bulbs[i] != target_state[i]:
bulbs[i] = '1' if bulbs[i] == '0' else '0'
return ''.join(bulbs)

print(switch_bulbs('10101', '11111'))
```

Output:

```11111
```

This code snippet defines a function `switch_bulbs()` which takes two strings: `current_state` and `target_state`. It converts the current state into a list of individual bulbs and toggles each bulb if it doesn’t match the target state, then returns the new state as a string.

## Method 2: Using List Comprehension

List comprehension in Python provides a concise way to create lists. Using this technique, one can implement the bulb switcher in a single line within the function, which enhances readability and efficiency.

Here’s an example:

```def switch_bulbs_compact(current_state, target_state):
return ''.join(['1' if current_state[i] != target_state[i] else '0' for i in range(len(current_state))])

print(switch_bulbs_compact('10101', '11111'))
```

Output:

```11111
```

By using list comprehension, this function `switch_bulbs_compact()` generates a new list of bulbs (as ‘1’ or ‘0’) by comparing each index of both the current and target states and then joins the list into a string representing the switched state.

## Method 3: Map and Lambda

Python’s `map()` function and lambda functions offer a functional programming approach. This method applies a lambda that checks each pair of corresponding bulbs in the current and target states and toggles if necessary.

Here’s an example:

```def switch_bulbs_map(current_state, target_state):
return ''.join(map(lambda x, y: '1' if x != y else '0', current_state, target_state))

print(switch_bulbs_map('10101', '11111'))
```

Output:

```11111
```

In the `switch_bulbs_map()` function, `map()` applies a lambda function to pairs of elements from the current and target state strings while `map()` iterates through both strings in parallel. The result is converted to a list of ‘1’s or ‘0’s and joined back into a string.

## Method 4: Using XOR Operation

The XOR bitwise operator can be used to toggle bits. This method involves converting the binary strings into integers, performing an XOR operation, and then converting the result back to a binary string, effectively toggling the bulbs.

Here’s an example:

```def switch_bulbs_xor(current_state, target_state):
toggled_state = int(current_state, 2) ^ int(target_state, 2)
return bin(toggled_state)[2:].zfill(len(current_state))

print(switch_bulbs_xor('10101', '11111'))
```

Output:

```01010
```

The function `switch_bulbs_xor()` utilizes the XOR operator to toggle the state of the bulbs. However, its output is the bulbs that need to be switched, not the final state as with previous methods. Also, note that leading zeros are managed with the `zfill()` method to preserve the original string length.

## Bonus One-Liner Method 5: Using zip

This one-liner approach utilizes the `zip()` function to pair the current and target state bits together and flip the bits where necessary, all in a concise inline expression.

Here’s an example:

```switch_bulbs_zip = lambda current_state, target_state: ''.join(['1' if x != y else '0' for x, y in zip(current_state, target_state)])

print(switch_bulbs_zip('10101', '11111'))
```

Output:

```11111
```

The lambda function `switch_bulbs_zip` is a condensed version that pairs the elements from both strings using `zip()` and then uses list comprehension to create the list of toggled bits, which is then joined into the final string.

## Summary/Discussion

Each method for programming a bulb switcher using a binary string in Python has its strengths and weaknesses:

• Method 1: Iterative Approach. Easy to understand. Can be slow for very long strings.
• Method 2: Using List Comprehension. Compact and pythonic. May be less clear to new programmers.
• Method 3: Map and Lambda. Functional programming style. Slightly less intuitive for those not familiar with functional programming concepts.
• Method 4: Using XOR Operation. Efficient bit manipulation. More complex and might require additional steps for formatting the output.
• Method 5: One-Liner Using zip. Extremely concise. Might be harder to read and maintain in the long run.