Python - Homework - Converting Any Base to Any Base
Solution 1:
This should be the first half of the answer to your problem. Can you figure out how to convert to a base?
# Create a symbol-to-value table.
SY2VA = {'0': 0,
'1': 1,
'2': 2,
'3': 3,
'4': 4,
'5': 5,
'6': 6,
'7': 7,
'8': 8,
'9': 9,
'A': 10,
'B': 11,
'C': 12,
'D': 13,
'E': 14,
'F': 15,
'G': 16,
'H': 17,
'I': 18,
'J': 19,
'K': 20,
'L': 21,
'M': 22,
'N': 23,
'O': 24,
'P': 25,
'Q': 26,
'R': 27,
'S': 28,
'T': 29,
'U': 30,
'V': 31,
'W': 32,
'X': 33,
'Y': 34,
'Z': 35,
'a': 36,
'b': 37,
'c': 38,
'd': 39,
'e': 40,
'f': 41,
'g': 42,
'h': 43,
'i': 44,
'j': 45,
'k': 46,
'l': 47,
'm': 48,
'n': 49,
'o': 50,
'p': 51,
'q': 52,
'r': 53,
's': 54,
't': 55,
'u': 56,
'v': 57,
'w': 58,
'x': 59,
'y': 60,
'z': 61,
'!': 62,
'"': 63,
'#': 64,
'$': 65,
'%': 66,
'&': 67,
"'": 68,
'(': 69,
')': 70,
'*': 71,
'+': 72,
',': 73,
'-': 74,
'.': 75,
'/': 76,
':': 77,
';': 78,
'<': 79,
'=': 80,
'>': 81,
'?': 82,
'@': 83,
'[': 84,
'\\': 85,
']': 86,
'^': 87,
'_': 88,
'`': 89,
'{': 90,
'|': 91,
'}': 92,
'~': 93}
# Take a string and base to convert to.
# Allocate space to store your number.
# For each character in your string:
# Ensure character is in your table.
# Find the value of your character.
# Ensure value is within your base.
# Self-multiply your number with the base.
# Self-add your number with the digit's value.
# Return the number.
def str2int(string, base):
integer = 0
for character in string:
assert character in SY2VA, 'Found unknown character!'
value = SY2VA[character]
assert value < base, 'Found digit outside base!'
integer *= base
integer += value
return integer
Here is the second half of the solution. By using these two functions, converting bases is very easy to do.
# Create a value-to-symbol table.
VA2SY = dict(map(reversed, SY2VA.items()))
# Take a integer and base to convert to.
# Create an array to store the digits in.
# While the integer is not zero:
# Divide the integer by the base to:
# (1) Find the "last" digit in your number (value).
# (2) Store remaining number not "chopped" (integer).
# Save the digit in your storage array.
# Return your joined digits after putting them in the right order.
def int2str(integer, base):
array = []
while integer:
integer, value = divmod(integer, base)
array.append(VA2SY[value])
return ''.join(reversed(array))
After putting it all together, you should end up with the program below. Please take time to figure it out!
innitvar = raw_input("Please enter a number: ")
basevar = int(raw_input("Please enter the base that your number is in: "))
convertvar = int(raw_input("Please enter the base that you would like to convert to: "))
# Create a symbol-to-value table.
SY2VA = {'0': 0,
'1': 1,
'2': 2,
'3': 3,
'4': 4,
'5': 5,
'6': 6,
'7': 7,
'8': 8,
'9': 9,
'A': 10,
'B': 11,
'C': 12,
'D': 13,
'E': 14,
'F': 15,
'G': 16,
'H': 17,
'I': 18,
'J': 19,
'K': 20,
'L': 21,
'M': 22,
'N': 23,
'O': 24,
'P': 25,
'Q': 26,
'R': 27,
'S': 28,
'T': 29,
'U': 30,
'V': 31,
'W': 32,
'X': 33,
'Y': 34,
'Z': 35,
'a': 36,
'b': 37,
'c': 38,
'd': 39,
'e': 40,
'f': 41,
'g': 42,
'h': 43,
'i': 44,
'j': 45,
'k': 46,
'l': 47,
'm': 48,
'n': 49,
'o': 50,
'p': 51,
'q': 52,
'r': 53,
's': 54,
't': 55,
'u': 56,
'v': 57,
'w': 58,
'x': 59,
'y': 60,
'z': 61,
'!': 62,
'"': 63,
'#': 64,
'$': 65,
'%': 66,
'&': 67,
"'": 68,
'(': 69,
')': 70,
'*': 71,
'+': 72,
',': 73,
'-': 74,
'.': 75,
'/': 76,
':': 77,
';': 78,
'<': 79,
'=': 80,
'>': 81,
'?': 82,
'@': 83,
'[': 84,
'\\': 85,
']': 86,
'^': 87,
'_': 88,
'`': 89,
'{': 90,
'|': 91,
'}': 92,
'~': 93}
# Take a string and base to convert to.
# Allocate space to store your number.
# For each character in your string:
# Ensure character is in your table.
# Find the value of your character.
# Ensure value is within your base.
# Self-multiply your number with the base.
# Self-add your number with the digit's value.
# Return the number.
integer = 0
for character in innitvar:
assert character in SY2VA, 'Found unknown character!'
value = SY2VA[character]
assert value < basevar, 'Found digit outside base!'
integer *= basevar
integer += value
# Create a value-to-symbol table.
VA2SY = dict(map(reversed, SY2VA.items()))
# Take a integer and base to convert to.
# Create an array to store the digits in.
# While the integer is not zero:
# Divide the integer by the base to:
# (1) Find the "last" digit in your number (value).
# (2) Store remaining number not "chopped" (integer).
# Save the digit in your storage array.
# Return your joined digits after putting them in the right order.
array = []
while integer:
integer, value = divmod(integer, convertvar)
array.append(VA2SY[value])
answer = ''.join(reversed(array))
# Display the results of the calculations.
print answer
Solution 2:
I need to multiply the leftmost digit in the initial number by its innitial base, and then add the next digit to the right, and then repeat until I hit the rightmost digit.
So you need to get digits. In a list.
Hint 1: Use divmod() function to break a number into digits. Divide by 10 to get decimal digits.
Hint 2: While n > 0: you can use divmod() to get a quotient and a remainder. If you save the remainder in the list, and use the quotient as the new value of n your number gets smaller until what's left is zero and you're done.
Hint 3: Your digits arrive in right-to-left order. Use reverse to switch the order of the list of this bothers you. Or create the list by using insert(0,digit).
Now that you have the digits. In a list. You can iterate through the list.
Try the for statement on for size.
You might need to use a "multiple and add" loop. total = total * new_base + next_digit is the way the body of the loop often looks.
Solution 3:
Just a Student, slow down with the idea of what you need. You may not need what you think you need.
Start at the beginning: the user inputs a number. The user inputs a base. These are both Strings. Say the base is 12, and the number is 1AB3. So you have a '1' in the 12^3 place, an 'A' in the 12^2 place, a 'B' in 12^1, and a '3' in the 12^0 (ones) place. If you want this number in base 10, you're going to need to add some numbers together.
Specifically, you need to add 1*12^3 + 10*12^2 + 11*12^1 + 3*12^0. Notice something here: you have 3,2,1,0. Which corresponds nicely to the LENGTH of the input string 1AB3. So probably a for loop would be helpful here. The user doesn't input an integer, they input a string. So you need the characters from the string, not the digits from the number.
How do you know what the symbols 'A' and 'C' represent in decimal notation? Look at the answer from Noctis Skytower!
So your first task is to figure out how to ITERATE THROUGH A STRING. Your second task is to figure out how to use the individual character values from your string to access the dictionary in Noctis Skytower's answer, and your third task is to figure out how to write a loop that takes advantage of that information.