Range Over Built in Python

Here we use range to sum the numbers in a list. Arrays work like this too.

nums = [2, 3, 4]
sum = 0
for num in nums:
    sum += num
print("sum:", sum)

range on lists provides both the index and value for each entry. Above we didn’t need the index, so we ignored it. Sometimes we actually want the indexes though.

for i, num in enumerate(nums):
    if num == 3:
        print("index:", i)

range on dictionaries iterates over key/value pairs.

kvs = {"a": "apple", "b": "banana"}
for k, v in kvs.items():
    print(f"{k} -> {v}")

range can also iterate over just the keys of a dictionary.

for k in kvs.keys():
    print("key:", k)

range on strings iterates over Unicode code points. The first value is the starting byte index of the rune and the second the rune itself.

for i, c in enumerate("go"):
    print(i, ord(c))

To run the program, you can simply execute the Python script.

$ python script.py
sum: 9
index: 1
a -> apple
b -> banana
key: a
key: b
0 103
1 111