windyboy
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- Added new images related to architecture and development. - Updated paths in various markdown files to correct resource locations. - Created new markdown files for Python development topics. - Deleted outdated and sensitive files, moving them to a secure archive. - Added a README for the security-sensitive files archive with recommendations for handling sensitive information.
37 lines
2.1 KiB
Markdown
37 lines
2.1 KiB
Markdown
Title: "\[Better Developers\] Using 'From X Import Y' in Python"
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Author: [[Reuven Lerner]]
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From:
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## Highlights:
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Is a variation on "import" that is commonly used, which looks like this:
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from X import Y
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The idea is pretty simple: When you say
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import foobar
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you're creating a variable "foobar" in the current namespace. That variable is a module, whose attributes are the global variables created in the module's file
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Whether you find it aesthetically ugly, or annoying to type, or confusing, or if you just want to put it in the current namespace, you can do that with:
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from foobar import hello
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Or if you want both of them, you can say
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from foobar import hello, x
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Once you have done this, the names "hello" and "x" are defined in your current namespace, and you can use them to access the module's attributes
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Note that I keep saying, "the current namespace." That's because "import", like "def", is a way to define a variable. When you use "def", you're both creating a function object and setting a variable (the function name) to point to that function object. And when you use "import", you're both creating a module object, and setting a variable (the module name) to point to that module object.
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But all variables can be global or local -- and modules are no different.
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I should note that while you can use an "import" statement anywhere, it's pretty rare in my experience to have it anywhere but at the global scope
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So: "from-import" loads the entire module, and puts the module in sys.modules. It then creates aliases to the specified names in the local namespace.
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And if you're using "from-import" because you want to save memory, or don't want to load an entire module, that's obviously bad news.
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When you say "from import *", you're saying that it would be totally OK for the module's variables to overwrite the variables that you have defined in the current namespace
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For starters, "from-import" ignores names that start with an underscore (_) character
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If I want, I can also define the variable __all__, a list of strings indicating which names should be exported when you use a wildcard |