python recursively convert decimal to hex
How would you recursively or iteratively change a decimal to hexadecimal?
I wrote a sample program that does not really work:
def ChangeHex(n):
if (n < 0):
print(0)
elif (n<=1):
print(n)
else:
ChangeHex(n / 16)
if (n == 15):
print("F")
if (n == 14):
print("E")
if (n == 13):
print("D")
if (n == 12):
print("C"开发者_JAVA技巧)
if (n == 11):
print("B")
if (n == 10):
print("A")
n % 16
How would I make it work properly? I know there is a built in function but I want to do it this way.
# Converts a decimal number to hexadecimal.
# Executes a zero-fill for up to six digits.
# This is used for correct conversion back
# to the instruction format. See zero_fill().
# @param dec Decimal representation of instruction
# @return Zero-filled hexadecimal instruction.
def convert(dec):
# BEGIN convert()
hex = "%X" % dec
return zero_fill(hex, 6)
# END convert()
# Prepends zeros until the specified
# length is reached. Works recursively.
# @param n Number to fill
# @param length Length to reach
# @return Zero-filled number
def zero_fill(n, length):
# BEGIN zero_fill()
# Check if length requirement is met
if len(n) != length:
# Requirement not met, run function again with
# n having one prepended zero.
return zero_fill('0'+n, length)
else:
# Requirement met, return n.
return n
# END zero_fill()
The main reason your program is not "working" is because you're misusing functions and immutable objects. Numbers objects are immutable, which means that you can't change the value of a number object in Python, you need to return a new number. And when you're doing ChangeHex(n)
, you passing the value of n
(i.e. the number object) to the function - it doesn't know that there is a variable that was associated with this number. And thus, when you change a local variable like n
, the the variable in the caller doesn't change.
You'd like the function to return a new value, not to try to change the one that's passed (which is not really possible). Look up the return statement, and use the value of ChangeHex(n)
. Hints:
result += ChangeHex(n)
return result
Probably you want to return what you're printing, but I can't really tell.
The same applies to operations. Since the numbers are immutable, an operations on numbers can't change the number, and you need to assign the number to a variable. n % 16
does nothing, you need assignment, like n = n % 16
or n %= 16
.
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