Convert Python3 to Python2

Question

I am trying to use finviz package (written for python 3) in my codes in Python 2. When importing I get SyntaxError:

    values = f'tickers: {tuple(self._tickers)}\n' \
                                                ^
SyntaxError: invalid syntax

The code in question looks like this in the library:

def __repr__(self):
    """ Returns a string representation of the parameter's values. """

    values = f'tickers: {tuple(self._tickers)}\n' \
             f'filters: {tuple(self._filters)}\n' \
             f'rows: {self._rows}\n' \
             f'order: {self._order}\n' \
             f'signal: {self._signal}\n' \
             f'table: {self._table}\n' \
             f'table: {self._custom}'

    return values

finviz's API is here and this part is in screener.py

Why are you writing new code for Python 2? It's going to be end-of-life as of the end of this year; no patches, even for security. Can you write everything in Python 3 and avoid this? 3to2 is a thing, but a package designed purely for Python 3 is unlikely to backport to Python 2 without some manual intervention. Point is, even if we solved this specific problem for you, the code is likely littered with other Python 3-only things (some of which won't be so obvious as to trigger SyntaxErrors, they might just silently misbehave). — ShadowRanger
– ShadowRanger, Commented May 22, 2019 at 0:23
I already have many codes in Python 2 and for now I am testing few things and not ready to migrate everything to Python 3. I tried 3to2 with no success. — Bob
– Bob, Commented May 22, 2019 at 0:27
Okay, but what I'm trying to tell you is that migrating 3.x-only packages back to Python 2 is usually going to be at least as much, if not more work, than migrating 2.x packages to Python 3. SyntaxErrors are obvious; subtleties in library usage, exception hierarchies, text/binary mismatches, etc. may not be caught at all, and spending your effort backporting to Python 2 rather than porting forward to Python 3 is a waste of limited resources. Either port to Python 3, or don't use finviz until you do. — ShadowRanger
– ShadowRanger, Commented May 22, 2019 at 0:54

catleeball · Accepted Answer · 2019-05-22 04:17:01Z

2

Python's f strings weren't introduced until 3.6.

A 2.x compatible way of interpolating strings with similar syntax is using str.format().

s = '{greeting}, {place}!'.format(greeting='Hello', place='World')
print s
>>> 'Hello, World!'

Or, here's what str.format might look like with your example:

values = ('tickers: {tickers}\n'
          'filters: {filters}\n'
          'rows: {rows}\n'
          'order: {order}\n'
          'signal: {signal}\n'
          'table: {table}\n'
          'table: {custom}'
)

values.format(
    tickers=tuple(self._tickers),
    filters=tuple(self._filters),
    rows=self._rows,
    order=self._order,
    signal=self._signal,
    table=self._table,
    custom=self._custom,
)

Here's the documentation for str.format()

edited May 22, 2019 at 4:17

answered May 22, 2019 at 0:34

catleeball

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Comments

Alec · Accepted Answer · 2019-05-22 00:47:51Z

2

You can replace f-strings with format like so:

f'{x} {y}' == '{}, {}!'.format(x, y)

But please don't! Python 2's life is over. It will receive no more updates, even for security, after 2020. It's better just to rewrite whatever you have in Python 2 to Python 3.

answered May 22, 2019 at 0:47

Alec

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1 Comment

Bob Over a year ago

It was useful to know.

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