Re: "no variable or argument declarations are necessary."

James A. Donald wrote: 
I am contemplating getting into Python, which is used by engineers I
admire - google and Bram Cohen, but was horrified to read

"no variable or argument declarations are necessary."

Surely that means that if I misspell a variable name, my program will
mysteriously fail to work with no error message.

If you don't declare variables, you can inadvertently re-use an
variable used in an enclosing context when you don't intend to, or
inadvertently reference a new variable (a typo) when you intended to
reference an existing variable.

What can one do to swiftly detect this type of bug?

A variable has to be assigned to before it is used, otherwise a NameError exception is thrown..

>>> a + 1
Traceback (most recent call last):
  File "<interactive input>", line 1, in ?
NameError: name 'a' is not defined
>>> a = 1
>>> a + 1
2

Typos in variable names are easily discovered unless the typo happens to exist in the current context.

Will McGugan
--
http://www.willmcgugan.com
"".join({'*':'@','^':'.'}.get(c,0) or chr(97+(ord(c)-84)%26) for c in "jvyy*jvyyzpthtna^pbz")
.

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