33 lines
2.0 KiB
Markdown
33 lines
2.0 KiB
Markdown
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---
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title: Python from X Import Y
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---
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If you have read the <a>`import statements`</a> wiki then you'd have seen me use this statement in one of the examples. Today, we'll try to understand what it does
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So picking up the same example:
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>>> from math import ceil, sqrt
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>>> # here it would be
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>>> sqrt(36)
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<<< 6
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 <a href='https://repl.it/CS5t/1' target='_blank' rel='nofollow'>Run Code</a>
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Or we could use this:
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>>> import math
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>>> # here it would be
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>>> math.sqrt(36)
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<<< 6
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 <a href='https://repl.it/CS5u' target='_blank' rel='nofollow'>Run Code</a>
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Then our code would look like`math.sqrt(x)` instead of `sqrt(x)`. This happens because when we use `import x`, a namespace `x` is itself created to avoid name conflicts. You have to access every single object of the module as `x.<name>`. But when we use `from x import y` we agree to add `y` to the main global namespace. So while using this we have to make sure that we don't have an object with same name in our program.
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> **Never use `from x import y` if an object named `y` already exists**
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For example, in `os` module there's a method `open`. But we even have a built-in function called `open`. So, here we should avoid using `from os import open`.
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We can even use `form x import *`, this would import all the methods, classes of that module to the global namespace of the program. This is a bad programming practice. Please avoid it.
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In general you should avoid ` from x import y` simply because of the problems it may cause in large scale programs. For example, you never know if a fellow programmer might want to make a new function that happens to be the name of one of the existing functions. You also do not know whether Python will change the library that you are importing functions from. While these problems won't exist as often for solo projects, as stated before, it is bad programming practice and should be avoided.
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