What do and mean in Python

Question

I notice that I can do things like 2  lt  lt  5 to get 64 and 1000  gt  gt  2 to get 250   Also I can use  gt  gt  in print   print  gt  gt obj   Hello world    What is happening here

User · Answer

The other case involving print  gt  gt obj   Hello World  is the  print chevron  syntax for the print statement in Python 2  removed in Python 3  replaced by the file argument of the print   function   Instead of writing to standard output  the output is passed to the obj write   method  A typical example would be file objects having a write   method  See the answer to a more recent question  Double greater-than sign in Python

User · Answer

They are bit shift operator which exists in many mainstream programming languages   lt  lt  is the left shift and  gt  gt  is the right shift  they can be demonstrated as the following table  assume an integer only take 1 byte in memory     operate   bit value   octal value                         description                            -------   ---------   -----------   --------------------------------------------------------               00000100              4                                                                4  lt  lt  2    00010000             16   move all bits to left 2 bits  filled with 0 at the right     16  gt  gt  2   00000100              4   move all bits to right 2 bits  filled with 0 at the left

User · Answer

12  lt  lt  2 48  Actual binary value of 12 is  quot 00 1100 quot  when we execute the above statement Left shift   2 places shifted left  returns the value 48 its binary value is  quot 11 0000 quot    48  gt  gt  2 12  The binary value of 48 is  quot 11 0000 quot   after executing above statement Right shift   2 places shifted right  returns the value 12 its binary value is  quot 00 1100 quot

User · Answer

lt  lt  Mean any given number will be multiply by 2the power for exp - 2 lt  lt 2 2 2 1 4           6 lt  lt 2 4 6 2 2 2 2 2 64

User · Answer

These are the shift operators     x  lt  lt  y Returns x with the bits shifted to the left by y places  and   new bits on the right-hand-side are zeros   This is the same as   multiplying x by 2  y        x    y Returns x with the bits shifted to the   right by y places  This is the same as    ing x by 2  y

User · Answer

These are bitwise shift operators   Quoting from the docs   x  lt  lt  y   Returns x with the bits shifted to the left by y places  and new bits on the right-hand-side are zeros   This is the same as multiplying x by 2  y   x  gt  gt  y   Returns x with the bits shifted to the right by y places  This is the same as dividing x by 2  y

User · Answer

I think it is important question and it is not answered yet  the OP seems to already know about shift operators   Let me try to answer  the    operator in your example is used for two different purposes  In c   terms this operator is overloaded  In the first example it is used as bitwise operator  left shift   while in the second scenario it is merely used as output redirection  i e   2  lt  lt  5   shift to left by 5 bits 2  gt  gt  5   shift to right by 5 bits print  gt  gt  obj   Hello world    redirect the output to obj     example  with open  foo txt    w   as obj      print  gt  gt  obj   Hello world    hello world now saved in foo txt   update   In python 3 it is possible to give the file argument directly as follows   print  Hello world   file open  foo txt    a      hello world now saved in foo txt

User · Answer

I verified the following on both Python 2 7 and Python 3 8 I did print 100 lt  lt 3  Converting 100 to Binary gives 1100100  What I did is I droped the first 3 bits and added 3 bits with the value  0  at the end  So it should result as 0100000  and I converted this to Decimal and the answer was 32  For my suprise when I executed print 100 lt  lt 3  the answer was 800  I was puzzled  I converted 800 to Binary to check whats going on  And this is what I got 1100100000  If you see how 800 was Python answer  they did not shift or drop the first 3 bits but they added value  0  to last 3 bits  Where as print 100 gt  gt 3    worked perfect  I did manual calculation and cheked the print result from python  It worked correctly  Dropped last 3 bits and added value  0  to first 3 bits  Looks like  100 lt  lt 3    left shift operator has a bug on Python

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