Python Basics: External Libraries

How does the following do?

from some_library import some_code

• Import the library some_library and rename it "some_code"

  _{(i.e. it is an alias)}

• Import "some_code" from some_library

  _{(it could be a function for example)}

• Raise an Exception

How does the following do?

import some_library as some_code

• Import the library some_library and rename it "some_code"

  _{(i.e. it is an alias)}

• Import "some_code" from some_library

  _{(it could be a function for example)}

• Raise an Exception

How does the following do?

from some_library import *

• Import the library some_library and rename it "*"

  _{(i.e. it is an alias)}

• Import everything from some_library and make it available directly

  _{(e.g. using "pi" instead of "math.pi")}

• Raise an Exception

What does the function say_hi do?

• Print Hello on the screen and return None

• Return a Path("Hello") _{(whatever that is)}

• Print Hello on the screen and return a Path("Hello")

• Raise an Exception

Answer explanation

This is a typical example of why it is dangerous to use Python keywords (print, list, dict, str...) as variable name or "alias" during import.

Here, we are replacing "print" with something else and you will have very weird behavior.

The libraries math and numpy both have a function "log": what will happen in the code of screenshot?

• An error because "log" is not found

• Print the value of log of 1000 base 10 from math library ... which is 3

• Trying to call log from numpy library and raise an Exception

• Raise an Error because we try to import log from both math and numpy

Answer explanation

☢️This is an example about why it is dangerous to do:

from a_module import *

It can over-write any function that is previously defined and lead to some weird behavior.

And that is why a lot of people recommend to never use "import *".

What happens after following line:

from math import pi, log

• You can use both math.pi and math.log

  _{e.g. print(math.pi, math.log(100, 10))}

• You can use both pi and log directly

  _{e.g. print(pi, log(100, 10))}

• Raise an Exception

Answer explanation

💡You can import several things inside a library by separating by a comma.