python - Changes in import statement python3 -

i don't understand following pep-0404

in python 3, implicit relative imports within packages no longer available - absolute imports , explicit relative imports supported. in addition, star imports (e.g. x import *) permitted in module level code.

what relative import? in other places star import allowed in python2? please explain examples.

relative import happens whenever importing package relative current script/package.

consider following tree example:

mypkg ├── base.py └── derived.py 

now, derived.py requires base.py. in python 2, (in derived.py):

from base import basething 

python 3 no longer supports since it's not explicit whether want 'relative' or 'absolute' base. in other words, if there python package named base installed in system, you'd wrong one.

instead requires use explicit imports explicitly specify location of module on path-alike basis. derived.py like:

from .base import basething 

the leading . says 'import base module directory'; in other words, .base maps ./base.py.

similarly, there .. prefix goes directory hierarchy ../ (with ..mod mapping ../mod.py), , ... goes 2 levels (../../mod.py) , on.

please note relative paths listed above relative directory current module (derived.py) resides in, not current working directory.

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@brenbarn has explained star import case. completeness, have same ;).

for example, need use few math functions use them in single function. in python 2 permitted semi-lazy:

def sin_degrees(x):     math import *     return sin(degrees(x)) 

note triggers warning in python 2:

a.py:1: syntaxwarning: import * allowed @ module level   def sin_degrees(x): 

in modern python 2 code should , in python 3 have either:

def sin_degrees(x):     math import sin, degrees     return sin(degrees(x)) 

or:

from math import *  def sin_degrees(x):     return sin(degrees(x))