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This problem has been getting at me for a while now. Is there an easier way to write nested for loops in python? For example if my code went something like this:
for y in range(3): for x in range(3): do_something() for y1 in range(3): for x1 in range(3): do_something_else() would there be an easier way to do this? I know that this code works but when you indent instead of using 2 spaces, like me, it can get to be a problem.
Oh in the example there were only 4 nested for loops to make things easier.
772
The outer loop can contain more than one inner loop. There is no limitation on the chaining of loops. In the nested loop, the number of iterations will be equal to the number of iterations in the outer loop multiplied by the iterations in the inner loop.
Microsoft BASIC had a nesting limit of 8. @Davislor: The error message refers to the stack size in the compiler, which is also a program, and which is recursively processing the nested-looped construct.
We can see that in the case of nested loops, list comprehensions are faster than the ordinary for loops, which are faster than while.
Nested For LoopsLoops can be nested in Python, as they can with other programming languages. The program first encounters the outer loop, executing its first iteration. This first iteration triggers the inner, nested loop, which then runs to completion.
If you're frequently iterating over a Cartesian product like in your example, you might want to investigate Python 2.6's itertools.product -- or write your own if you're in an earlier Python.
from itertools import product for y, x in product(range(3), repeat=2): do_something() for y1, x1 in product(range(3), repeat=2): do_something_else() This is fairly common when looping over multidimensional spaces. My solution is:
xy_grid = [(x, y) for x in range(3) for y in range(3)] for x, y in xy_grid: # do something for x1, y1 in xy_grid: # do something else If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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