python - What does base value do in int function? -
i've read official doc https://docs.python.org/2/library/functions.html#int, still confused.
i've tried command on terminal, find rules, still not quite clear it. hope more knowledge can explain further.
below examples , findings:
int('0', base=1) valueerror: int() base must >= 2 , <=36 int('3', base=2) valueerror: invalid literal int() base 2: int('3', base=4) 3 int('33', base=4) 15 int('333', base=4) 63 int('353', base=4) valueerror: invalid literal int() base 4: i find 2 rules here:
- the single string numbers must smaller base number.
- the
int()return number equals(n)*(base^(n-1)) + (n-1)*(base^(n-2)) + ... + 1*(base^0)
are there other hidden rules this, , kind of problem base designed solve?
it says - converts string integer in given numeric base. per documentation, int() can convert strings in base 2 36. on low end, base 2 lowest useful system; base 1 have "0" symbol, pretty useless counting. on high end, 36 chosen arbitrarily because use symbols "0123456789abcdefghijklmnopqrstuvwxyz" (10 digits + 26 characters) - continue more symbols, not clear use after z.
"normal" math base-10 (uses symbols "0123456789"):
int("123", 10) # == 1*(10**2) + 2*(10**1) + 3*(10**0) == 123 binary base-2 (uses symbols "01"):
int("101", 2) # == 1*(2**2) + 0*(2**1) + 1*(2**0) == 5 "3" makes no sense in base 2; uses symbols "0" , "1", "3" invalid symbol (it's kind of trying book appointment 34th of january).
int("333", 4) # == 3*(4**2) + 3*(4**1) + 3*(4**0) # == 3*16 + 3*4 + 3*1 # == 48 + 12 + 3 # == 63 
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