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<div dir="ltr">mypy currently
inspects the comment on the line of first assignment for the
variables to be type hinted.
<p style="margin-bottom:0cm;line-height:100%">It is logical
that
at some time python language will add support to allow
these type
hints to move from comments to the code as has happened
for 'def'
signatures.
</p>
<p style="margin-bottom:0cm;line-height:100%">One logical
syntax
would be to move from
</p>
<pre>i = 1 # Infer type int for i</pre>
<p style="margin-bottom:0cm;line-height:100%">
to</p>
<pre>i:int = 1 # no comment needed, but does not look attractive
<span style="font-family:arial,sans-serif">The first question that arises is 'is the type inference legal for the additional uses. Having a 'second use' flagged by warning or error by either an external typechecker or even the language itself could pick up on accidental reuse of a name, but in practice accidentally creating a new variable through a typo can be more common.
In python today the first use is the same as every other, so this change just does not feel comfortable.
The other question is 'what about globals and nonlocals?'. Currently globals and nonlocals need a 'global' or 'nonlocal' statement to allow assignment, but what if these values are not assigned in scope?
What if we allowed </span>
global i:int</pre>
<p style="margin-bottom:0cm;line-height:100%">or </p>
<pre style="margin-bottom:0cm;line-height:100%"><span style="font-family:courier new,monospace">nonlocal i:int</span></pre>
<p style="margin-bottom:0cm;line-height:100%">and even
</p>
<pre style="margin-bottom:0cm;line-height:100%"><span style="font-family:courier new,monospace">local i:int</span></pre>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"><font size="2">Permitting
a new
keyword 'local' to me might bring far more symmetry
between different
cases.</font></span>
</p>
<span style="font-family:arial,sans-serif"><font size="2"></font></span>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"><font size="2">It
would also allow
type hinting to be collected near the function
definition and keep
the type hinting clear of the main code.</font></span></p>
<span style="font-family:arial,sans-serif"><font size="2">
</font></span>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"><font size="2">Use
of the 'local'
keyword in the global namespace could indicate a value
not accessible
in other namespaces.</font></span></p>
<span style="font-family:arial,sans-serif"><font size="2">
</font></span><span style="font-family:arial,sans-serif"><font
size="2">
</font></span>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"><font size="2">Personally
I would
like to go even further and allow some syntax to allow
(or disable)
flagging the use of new variables without type hinting
as possible
typos</font></span></p>
<span style="font-family:arial,sans-serif"><font size="2">
</font></span>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"></span><span
style="font-family:arial,sans-serif"></span><span
style="font-family:arial,sans-serif"><font size="2">I
have a syntax in
mind, but the idea is the discussion point, not the
specific syntax.</font></span><span
style="font-family:arial,sans-serif"></span></p>
<p style="margin-bottom:0cm;line-height:100%"><span
style="font-family:arial,sans-serif"><font size="2">Possibly
what is here already is too much of a change of
direction to consider for ideas already in progress?<br>
</font></span></p>
<span style="font-family:arial,sans-serif"><font size="2">
</font></span>
<p style="margin-bottom:0cm;line-height:100%"><br>
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