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The Python range() function returns a sequence of numbers. It is commonly used as part of a for loop.

range(start, stop, step)

  • start – optional, default is 0
  • stoprequired
  • step – optional, default is 1

Loop pattern

The range() function is commonly used to loop over some code a specific number of times.

for i in range(10):

The above code will print each number in the range [0, 9] inclusive. Note that range(10) begins at 0 and stops at 9 – a total of 10 numbers but not including the number 10.

Multiple parameters

range() may be called with a single bounding parameter, as in range(stop). The returned sequence will begin at zero and count up by 1 until the bound (not including it). For example, range(4) would include 0, 1, 2, and 3, but not 4.

When using two parameters, the function operates as range(start, stop). The start parameter specifies the first number of the sequence, and stop works as before by bounding the sequence. So range(2, 5) would include 2, 3, and 4, but not 5.

Finally, a function call with three parameters is done by range(start, stop, step). The step parameter specifies the incrementation between each consecutive number in the sequence, beginning at the starting number. As an example, range(0, 6, 2) would include 0, 2, and 4 (6 is the upper bound, so is not included).