How to strip off left side of binary number in Python?

I got this binary number 101111111111000

I need to strip off the 8 most significant bits and have 11111000 at the end.

I tried to make 101111111111000 << 8, but this results in 10111111111100000000000, it hasn't the same effect as >> which strips the lower bits. So how can this be done? The final result MUST BE binary type.

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

2

What do you mean by "binary type"? Python has no such type. Would an integer suffice?

– Rory Daulton
Nov 25 '18 at 22:39

"it hasn't the same effect as >> which strips the lower bits" is because >> does not "strip", but it shifts the bits. So it does have the same effect as <<, in the other direction.

– usr2564301
Nov 25 '18 at 22:40

Integers are binary yeah, but I'am working in the binary level, that's why i'am approaching it with binaries.

– Rodrigo Formighieri
Nov 25 '18 at 22:41

1

@Alnitak It would be more like I need the 8 lower significant bits of any binary number, doesnt matter the word length.

– Rodrigo Formighieri
Nov 25 '18 at 22:52

1

@RodrigoFormighieri that's a completely different (but far easier) question to answer. Your question would have made more sense if you had described what you wanted to retain rather than what you want to throw away.

– Alnitak
Nov 25 '18 at 23:00

|
show 1 more comment

I got this binary number 101111111111000

I need to strip off the 8 most significant bits and have 11111000 at the end.

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

2

What do you mean by "binary type"? Python has no such type. Would an integer suffice?

– Rory Daulton
Nov 25 '18 at 22:39

"it hasn't the same effect as >> which strips the lower bits" is because >> does not "strip", but it shifts the bits. So it does have the same effect as <<, in the other direction.

– usr2564301
Nov 25 '18 at 22:40

Integers are binary yeah, but I'am working in the binary level, that's why i'am approaching it with binaries.

– Rodrigo Formighieri
Nov 25 '18 at 22:41

1

@Alnitak It would be more like I need the 8 lower significant bits of any binary number, doesnt matter the word length.

– Rodrigo Formighieri
Nov 25 '18 at 22:52

1

@RodrigoFormighieri that's a completely different (but far easier) question to answer. Your question would have made more sense if you had described what you wanted to retain rather than what you want to throw away.

– Alnitak
Nov 25 '18 at 23:00

|
show 1 more comment

I got this binary number 101111111111000

I need to strip off the 8 most significant bits and have 11111000 at the end.

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

I got this binary number 101111111111000

I need to strip off the 8 most significant bits and have 11111000 at the end.

python binary

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

asked Nov 25 '18 at 22:35

Rodrigo Formighieri

1109

2

What do you mean by "binary type"? Python has no such type. Would an integer suffice?

– Rory Daulton
Nov 25 '18 at 22:39

"it hasn't the same effect as >> which strips the lower bits" is because >> does not "strip", but it shifts the bits. So it does have the same effect as <<, in the other direction.

– usr2564301
Nov 25 '18 at 22:40

Integers are binary yeah, but I'am working in the binary level, that's why i'am approaching it with binaries.

– Rodrigo Formighieri
Nov 25 '18 at 22:41

1

@Alnitak It would be more like I need the 8 lower significant bits of any binary number, doesnt matter the word length.

– Rodrigo Formighieri
Nov 25 '18 at 22:52

1

@RodrigoFormighieri that's a completely different (but far easier) question to answer. Your question would have made more sense if you had described what you wanted to retain rather than what you want to throw away.

– Alnitak
Nov 25 '18 at 23:00

|
show 1 more comment

2

What do you mean by "binary type"? Python has no such type. Would an integer suffice?

– Rory Daulton
Nov 25 '18 at 22:39

"it hasn't the same effect as >> which strips the lower bits" is because >> does not "strip", but it shifts the bits. So it does have the same effect as <<, in the other direction.

– usr2564301
Nov 25 '18 at 22:40

Integers are binary yeah, but I'am working in the binary level, that's why i'am approaching it with binaries.

– Rodrigo Formighieri
Nov 25 '18 at 22:41

1

@Alnitak It would be more like I need the 8 lower significant bits of any binary number, doesnt matter the word length.

– Rodrigo Formighieri
Nov 25 '18 at 22:52

1

@RodrigoFormighieri that's a completely different (but far easier) question to answer. Your question would have made more sense if you had described what you wanted to retain rather than what you want to throw away.

– Alnitak
Nov 25 '18 at 23:00

What do you mean by "binary type"? Python has no such type. Would an integer suffice?

– Rory Daulton
Nov 25 '18 at 22:39

"it hasn't the same effect as >> which strips the lower bits" is because >> does not "strip", but it shifts the bits. So it does have the same effect as <<, in the other direction.

– usr2564301
Nov 25 '18 at 22:40

Integers are binary yeah, but I'am working in the binary level, that's why i'am approaching it with binaries.

– Rodrigo Formighieri
Nov 25 '18 at 22:41

@Alnitak It would be more like I need the 8 lower significant bits of any binary number, doesnt matter the word length.

– Rodrigo Formighieri
Nov 25 '18 at 22:52

@RodrigoFormighieri that's a completely different (but far easier) question to answer. Your question would have made more sense if you had described what you wanted to retain rather than what you want to throw away.

– Alnitak
Nov 25 '18 at 23:00

|
show 1 more comment

3 Answers
3

active

oldest

votes

You can get the rightmost 8 bits of an integer n using bitwise-and:

n&255

255 is the sum of the values of the smallest 8 bits.

So, starting with 101111111111000, which is 24568 decimal, n&255 gives 11111000, which is 248 decimal.

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

add a comment |

another general way to do this is:

n = int('101111111111000', 2) # 24568



n & (1 << int.bit_length(n) - 8) - 1

gives 120 (or 1111000)

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

add a comment |

To achieve this for a number x with n digits, one can use this

x&(2**(len(bin(x))-2-8)-1)

-2 to strip 0b, -8 to strip leftmost

Simply said it ands your number with just enough 1s that the 8 leftmost bits are set to 0.

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

add a comment |

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3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

You can get the rightmost 8 bits of an integer n using bitwise-and:

n&255

255 is the sum of the values of the smallest 8 bits.

So, starting with 101111111111000, which is 24568 decimal, n&255 gives 11111000, which is 248 decimal.

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

add a comment |

You can get the rightmost 8 bits of an integer n using bitwise-and:

n&255

255 is the sum of the values of the smallest 8 bits.

So, starting with 101111111111000, which is 24568 decimal, n&255 gives 11111000, which is 248 decimal.

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

add a comment |

You can get the rightmost 8 bits of an integer n using bitwise-and:

n&255

255 is the sum of the values of the smallest 8 bits.

So, starting with 101111111111000, which is 24568 decimal, n&255 gives 11111000, which is 248 decimal.

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

You can get the rightmost 8 bits of an integer n using bitwise-and:

n&255

255 is the sum of the values of the smallest 8 bits.

So, starting with 101111111111000, which is 24568 decimal, n&255 gives 11111000, which is 248 decimal.

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

edited Nov 25 '18 at 22:44

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

answered Nov 25 '18 at 22:38

khelwood

31.9k74465

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

add a comment |

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

this is only consistent with the OP's question if the input data had 16 bits to start with.

– Alnitak
Nov 25 '18 at 22:44

Well possibly. The OP said they wanted to strip the first 8 bits off a 15 bit number, but the output they asked for was 8 bits, so it doesn't seem like that was quite what they wanted.

– khelwood
Nov 25 '18 at 22:49

add a comment |

another general way to do this is:

n = int('101111111111000', 2) # 24568



n & (1 << int.bit_length(n) - 8) - 1

gives 120 (or 1111000)

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

add a comment |

another general way to do this is:

n = int('101111111111000', 2) # 24568



n & (1 << int.bit_length(n) - 8) - 1

gives 120 (or 1111000)

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

add a comment |

another general way to do this is:

n = int('101111111111000', 2) # 24568



n & (1 << int.bit_length(n) - 8) - 1

gives 120 (or 1111000)

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

another general way to do this is:

n = int('101111111111000', 2) # 24568



n & (1 << int.bit_length(n) - 8) - 1

gives 120 (or 1111000)

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

answered Nov 25 '18 at 23:18

Sam Mason

3,35811331

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

add a comment |

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

Also works! Thanks

– Rodrigo Formighieri
Nov 26 '18 at 12:43

add a comment |

To achieve this for a number x with n digits, one can use this

x&(2**(len(bin(x))-2-8)-1)

-2 to strip 0b, -8 to strip leftmost

Simply said it ands your number with just enough 1s that the 8 leftmost bits are set to 0.

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

add a comment |

To achieve this for a number x with n digits, one can use this

x&(2**(len(bin(x))-2-8)-1)

-2 to strip 0b, -8 to strip leftmost

Simply said it ands your number with just enough 1s that the 8 leftmost bits are set to 0.

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

add a comment |

To achieve this for a number x with n digits, one can use this

x&(2**(len(bin(x))-2-8)-1)

-2 to strip 0b, -8 to strip leftmost

Simply said it ands your number with just enough 1s that the 8 leftmost bits are set to 0.

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

To achieve this for a number x with n digits, one can use this

x&(2**(len(bin(x))-2-8)-1)

-2 to strip 0b, -8 to strip leftmost

Simply said it ands your number with just enough 1s that the 8 leftmost bits are set to 0.

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

answered Nov 25 '18 at 23:05

Jonathan R

1,182512

add a comment |

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