>>> x = "2342.34"
>>> float(x)
2342.3400000000001
There you go. Use float (which behaves like and has the same precision as a C,C++, or Java double).
Answer from Mongoose on Stack OverflowHow do I convert a string to a double in Python? - Stack Overflow
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TIL a Python float is the same (precision) as a Java double
Double precision
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>>> x = "2342.34"
>>> float(x)
2342.3400000000001
There you go. Use float (which behaves like and has the same precision as a C,C++, or Java double).
The decimal operator might be more in line with what you are looking for:
>>> from decimal import Decimal
>>> x = "234243.434"
>>> print Decimal(x)
234243.434
TL;DR in Java a "double" is a 64-bit float and a "float" is a 32-bit float; in Python a "float" is a 64-bit float (and thus equivalent to a Java double). There doesn't appear to be a natively implemented 32-bit float in Python (I know numpy/pandas has one, but I'm talking about straight vanilla Python with no imports).
In many programming languages, a double variable type is a higher precision float and unless there was a performance reason, you'd just use double (vs. a float). I'm almost certain early in my programming "career", I banged my head against the wall because of precision issues while using floats thus I avoided floats like the plague.
In other languages, you need to type a variable while declaring it.
Java: int age=30
Python: age=30
As Python doesn't have (or require?) typing a variable before declaring it, I never really thought about what the exact data type was when I divided stuff in Python, but on my current project, I've gotten in the habit of hinting at variable type for function/method arguments.
def do_something(age: int, name: str):
I could not find a double data type in Python and after a bunch of research it turns out that the float I've been avoiding using in Python is exactly a double in Java (in terms of precision) with just a different name.
Hopefully this info is helpful for others coming to Python with previous programming experience.
P.S. this is a whole other rabbit hole, but I'd be curious as to the original thought process behind Python not having both a 32-bit float (float) and 64-bit float (double). My gut tells me that Python was just designed to be "easier" to learn and thus they wanted to reduce the number of basic variable types.
Hi everyone!
I recently started a project with Python and after long weeks of writing code, I saw that Python's default float precision is just not enough for my needs.
Is there a simple way to change the default Python precision without having to rewrite all my code?
Thank you all in advance!
Python's built-in float type has double precision (it's a C double in CPython, a Java double in Jython). If you need more precision, get NumPy and use its numpy.float128.
Decimal datatype
- Unlike hardware based binary floating point, the decimal module has a user alterable precision (defaulting to 28 places) which can be as large as needed for a given problem.
If you are pressed by performance issuses, have a look at GMPY