How to start a for loop at 1 - Python

Python for loops range typically starts at 0. However, there are cases where starting the loop at 1 is more intuitive or necessary such as when dealing with 1-based indexing in mathematics or user-facing applications.

Let's see some methods to start a for loop at 1 in Python.

Using range() with a Start Parameter

range() function allows us to specify a start, stop, and step. By default, it starts at 0 but we can specify 1 as the starting point.

# Loop starting at 1

for i in range(1, 6):  # Loop from 1 to 5

    print("Current number:", i)

The range(1, 6) specifies a start of 1 and goes up to 5 (excluding 6 as range is non-inclusive), this is the simplest and most common way to start a loop at 1.

Let's explore some other methods to start a for loop at 1.

Using a List or Sequence Starting at 1

If we have a predefined sequence such as a list starting at 1 then we can iterate directly over it.

# Predefined list
numbers = [1, 2, 3, 4, 5]

for num in numbers:
    print("Current number:", num)

In this example, the list numbers starts at 1 so the loop iterates directly over the elements without needing range.

Using Enumerated Loop Starting at 1

If we are iterating over a collection but need an index that starts at 1 the enumerate() function is useful. It has an optional start parameter to specify the starting index.

# List of items

items = ["apple", "banana", "cherry"]

for idx, item in enumerate(items, start=1):

    print(f"Item {idx}: {item}")

enumerate(items, start=1) provides an index starting at 1 while iterating over the list.

Manually Incrementing a Variable

In scenarios where a loop inherently starts at 0 we can initialize a counter variable at 1 and increment it manually.

# Initialize counter

start = 1

for _ in range(5):  # Loop 5 times

    print("Current number:", start)

    start += 1

The start variable begins at 1 and is manually incremented in each iteration