Create a list of coordinate pairs via nested iteration.

Express a concise way to produce a grid of index pairs for iteration or indexing.

When needing to iterate over a 2D grid, generate coordinate lists, or prepare data for nested loops.

Used in list comprehensions, matrix initialization, combinatorial generation, simulation loops.

[(i, j) for i in range(A) for j in range(B)]

[(i, j) for i in range(X) for j in range(Y)]

i, j: variable names; A, B: integer range limits or variables.

• range
• list
• tuple
• for
• in
• list comprehension

• i
• j can be any identifier
• range limits can be any integer expression or variable.

Missing parentheses around tuple, swapping loop order unintentionally, using incorrect range arguments.

[(i, j) for i in range(2) for j in range(3)] (swapped dimensions) vs. [(i, j) for i in range(3) for j in range(2)] (original).

Confusing loop order; mistaking list comprehension for generator expression (parentheses vs brackets).

• list comprehensions

The outer loop variable changes slower than the inner; loop order determines tuple ordering.

Signals intent to produce a structured list of pairs efficiently.

Picture a 3‑row by 2‑column grid.

Common idiom for generating coordinate grids; equivalent to list(itertools.product(range(3), range(2))).

Consider using itertools.product for readability or numpy.meshgrid for numeric grids.