Cross-File Name Changes

Recall from the preceding example that the assignment to x in the interactive session changed the name x in that scope only, not the x in the file—there is no link from a name copied with from back to the file it came from. To really change a global name in another file, you must use import:

% python
>>> from small import x, y         # Copy two names out
>>> x = 42                         # Changes my x only

>>> import small                   # Get module name
>>> small.x = 42                   # Changes x in other module

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This phenomenon was introduced in Chapter 17. Because changing variables in other modules like this is a common source of confusion (and often a bad design choice), we’ll revisit this technique again later in this part of the book. Note that the change to y[0] in the prior session is different; it changes an object, not a name.