将十六进制函数修饰为垫零

我写了这个简单的函数:

def padded_hex(i, l):
given_int = i
given_len = l


hex_result = hex(given_int)[2:] # remove '0x' from beginning of str
num_hex_chars = len(hex_result)
extra_zeros = '0' * (given_len - num_hex_chars) # may not get used..


return ('0x' + hex_result if num_hex_chars == given_len else
'?' * given_len if num_hex_chars > given_len else
'0x' + extra_zeros + hex_result if num_hex_chars < given_len else
None)

例子:

padded_hex(42,4) # result '0x002a'
hex(15) # result '0xf'
padded_hex(15,1) # result '0xf'

虽然这对我来说已经足够清楚了，并且适合我的用例(一个简单打印机的简单测试工具) ，但我还是忍不住想还有很多改进的空间，这可以压缩成一些非常简洁的东西。

解决这个问题还有哪些其他方法？

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How about this:

print '0x%04x' % 42
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最佳答案

Use the new .format() string method:

>>> "{0:#0{1}x}".format(42,6)
'0x002a'

Explanation:

{   # Format identifier
0:  # first parameter
#   # use "0x" prefix
0   # fill with zeroes
{1} # to a length of n characters (including 0x), defined by the second parameter
x   # hexadecimal number, using lowercase letters for a-f
}   # End of format identifier

If you want the letter hex digits uppercase but the prefix with a lowercase 'x', you'll need a slight workaround:

>>> '0x{0:0{1}X}'.format(42,4)
'0x002A'

Starting with Python 3.6, you can also do this:

>>> value = 42
>>> padding = 6
>>> f"{value:#0{padding}x}"
'0x002a'
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Use * to pass width and X for uppercase

print '0x%0*X' % (4,42) # '0x002A'

As suggested by georg and Ashwini Chaudhary

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If just for leading zeros, you can try zfill function.

'0x' + hex(42)[2:].zfill(4) #'0x002a'
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Suppose you want to have leading zeros for hexadecimal number, for example you want 7 digit where your hexadecimal number should be written on, you can do like that : 

hexnum = 0xfff
str_hex =  hex(hexnum).rstrip("L").lstrip("0x") or "0"
'0'* (7 - len(str_hexnum)) + str_hexnum

This gives as a result : 

'0000fff'
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If you don't need to handle negative numbers, you can do

"{:02x}".format(7)   # '07'
"{:02x}".format(27)  # '1b'

Where

  • : is the start of the formatting specification for the first argument {} to .format()
  • 02 means "pad the input from the left with 0s to length 2"
  • x means "format as hex with lowercase letters"

You can also do this with f-strings:

f"{7:02x}"   # '07'
f"{27:02x}"  # '1b'
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None of the answers are dealing well with negative numbers...
Try this:

val = 42
nbits = 16
'{:04X}'.format(val & ((1 << nbits)-1))

enter image description here

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If you want to hold the preceding hex notation 0x you can also try this method too which is using the python3 f-strings.

    f'0x{10:02x}' # 0x0a

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