Current File : //lib/python3/dist-packages/pythran/transformations/remove_fstrings.py
"""Turns f-strings to format syntax with modulus"""
import gast as ast
from pythran.passmanager import Transformation
from pythran.syntax import PythranSyntaxError
class RemoveFStrings(Transformation, ast.NodeTransformer):
"""Turns f-strings to format syntax with modulus
>>> import gast as ast
>>> from pythran import passmanager, backend
>>> node = ast.parse("f'a = {1+1:4d}; b = {b:s};'")
>>> pm = passmanager.PassManager("test")
>>> _, node = pm.apply(RemoveFStrings, node)
>>> print(pm.dump(backend.Python, node))
('a = %4d; b = %s;' % ((1 + 1), b))
"""
def visit_JoinedStr(self, node):
if len(node.values) == 1 and not isinstance(
node.values[0], ast.FormattedValue
):
# f-strings with no reference to variable (like `f"bar"`, see #1767)
return node.values[0]
if not any(
isinstance(value, ast.FormattedValue) for value in node.values
):
# nothing to do (not a f-string)
return node
base_str = ""
elements = []
for value in node.values:
if isinstance(value, ast.Constant):
base_str += value.value.replace("%", "%%")
elif isinstance(value, ast.FormattedValue):
base_str += "%"
if value.format_spec is None:
raise PythranSyntaxError(
"f-strings without format specifier not supported", value
)
base_str += value.format_spec.values[0].value
elements.append(value.value)
else:
raise NotImplementedError
return ast.BinOp(
left=ast.Constant(value=base_str, kind=None),
op=ast.Mod(),
right=ast.Tuple(elts=elements, ctx=ast.Load()),
)
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