Does '!=' equivelent to 'is not'

[pirata]

I'm a bit confusing about whether "is not" equivelent to "!="

if a != b:
  ...

if a is not b:
  ...


What's the difference between "is not" and "!=" or they are the same thing?
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print problem

[pirata]

I was trying to print a dot on console every second to indicates
running process, so I wrote, for example:

for i in xrange(10):
print ".",
time.sleep(1)

Idealy, a dot will be printed out each second. But there is nothing 
print out until after 10 seconds, all 10 dots come out together.

I've tried lose the comma in the print statement, and it works.

Is that because of the print statement buffer the characters until 
there is a new line character?

Thanks
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