Ian D wrote:
Ian, please answer to the list, not me in private. Thank you.
> Most of this makes sense except for the c(a<=b)
> also
> if c(a<=b)
>
> It is the c(...) syntax that I don't understand.
>
> I dont recall seeing a statement like this.
c is just an arbitrary function, I put in the three dots as a placeholder
for the actual arguments. A concrete example would be
# python2: use raw_input(), not input()
a = float(input("enter a float "))
b = float(input("enter another float "))
if abs(a - b) > 1.0:
print("Your numbers are more than 1.0 apart.")
Here
abs(a-b) > 1.0
is the conditional expression. It is in turn built of the comparison
x > 1.0
where x
is the function call
abs(z)
where z is the arithmetic expression
a - b
PS: Fun fact: three dots may occur in actual Python code:
>>> def f(x): return x
...
>>> f(...) # python 3 only
Ellipsis
The only place I know where this is commonly used is the numpy library:
>>> import numpy
>>> a = numpy.array(range(1, 5)).reshape((2,2))
>>> a
array([[1, 2],
[3, 4]])
>>> a[0]
array([1, 2])
>>> a[...,1] # python 2 and 3
array([2, 4])
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