python - What is the function of elif? -

if wanted check multiple conditions, can't use multiple if statements? example:

a = 10 b = 20 if == b:   print('equal') if < b:   print('less') if > b:   print('greater') 

using multiple if statements evaluate every if condition. conditions in example mutual exclusive, might have similar result. however, if a or b changes in-between, condition might become true:

a = 5 b = 7 if < b:     = b if == b:     b += 1 

both conditions evalute true , executed. might not intended, use:

a = 5 b = 7 if < b:     = b elif == b:     b += 1     

will execute first condition.

even mutual exclusive conditions example, every expression has evaluated, slower second variant.

note elif (aka else if) identical to:

if <cond1>:     pass else:     if <cond2>:         pass     else:         if <cond3>:             pass 

as can see, result in tests run out of text , less readable than:

if <cond1>:     pass elif <cond2>:     pass ... 

this more expressive, reader has not check conditions mutual exclusive. semantics clear beginning.

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finally:

something like:

i = 1 if none:     k = 5 elif not (i <= 0):     k = 

will not work using example.