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# Binary Search

## Create Sorted List

```
sorted_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20]
print(sorted_list)
```

```
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20]
```

## Create Binary Search Algorithm

```
def binary_search(sorted_list, target):
'''This function inputs a sorted list and a target value to find and returns ....'''
# Create variables for the index of the first and last elements
start = 0
end = len(sorted_list) - 1
while end >= start:
# Create a variable for the index of the middle term
middle = start + (end - start) // 2 # // is integer division in Python 3.X
# If the target value is less than the middle value of the search area
if target < sorted_list[middle]:
# Cut the list in half by making the new end value the old middle value minus 1
# The minus one is because we already ruled the middle value out, so we can ignore it
end = middle - 1
# Else, if the target value is greater than the middle value of the search area
elif target > sorted_list[middle]:
# Cut the list in half by making the new start value the old middle value plus 1
# The plus one is because we already ruled the middle value out, so we can ignore it
start = middle + 1
# If it's not too high or too low, it must be just right, return the location
else:
return ("Found it at index: {}".format(middle))
# If we've fallen out of the while loop the target value is not in the list
return print("Not in list!")
```

## Conduct Binary Search

```
# Run binary search
binary_search(sorted_list, 2)
```

```
'Found it at index: 1'
```

Thanks for Julius for the improved code.