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我想使用AST python模塊將python數學表達式轉換爲postfix表示法。這是我走到這一步:如何使用AST python模塊將infix轉換爲postfix/prefix?
import parser
import ast
from math import sin, cos, tan
formulas = [
"1+2",
"1+2*3",
"1/2",
"(1+2)*3",
"sin(x)*x**2",
"cos(x)",
"True and False",
"sin(w*time)"
]
class v(ast.NodeVisitor):
def __init__(self):
self.tokens = []
def f_continue(self, node):
super(v, self).generic_visit(node)
def visit_Add(self, node):
self.tokens.append('+')
self.f_continue(node)
def visit_And(self, node):
self.tokens.append('&&')
self.f_continue(node)
def visit_BinOp(self, node):
# print('visit_BinOp')
# for child in ast.iter_fields(node):
# print(' child %s ' % str(child))
self.f_continue(node)
def visit_BoolOp(self, node):
# print('visit_BoolOp')
self.f_continue(node)
def visit_Call(self, node):
# print('visit_Call')
self.f_continue(node)
def visit_Div(self, node):
self.tokens.append('/')
self.f_continue(node)
def visit_Expr(self, node):
# print('visit_Expr')
self.f_continue(node)
def visit_Import(self, stmt_import):
for alias in stmt_import.names:
print('import name "%s"' % alias.name)
print('import object %s' % alias)
self.f_continue(stmt_import)
def visit_Load(self, node):
# print('visit_Load')
self.f_continue(node)
def visit_Module(self, node):
# print('visit_Module')
self.f_continue(node)
def visit_Mult(self, node):
self.tokens.append('*')
self.f_continue(node)
def visit_Name(self, node):
self.tokens.append(node.id)
self.f_continue(node)
def visit_NameConstant(self, node):
self.tokens.append(node.value)
self.f_continue(node)
def visit_Num(self, node):
self.tokens.append(node.n)
self.f_continue(node)
def visit_Pow(self, node):
self.tokens.append('pow')
self.f_continue(node)
for index, f in enumerate(formulas):
print('{} - {:*^76}'.format(index, f))
visitor = v()
visitor.visit(ast.parse(f))
print(visitor.tokens)
print()
# 0 - ************************************1+2*************************************
# [1, '+', 2]
# 1 - ***********************************1+2*3************************************
# [1, '+', 2, '*', 3]
# 2 - ************************************1/2*************************************
# [1, '/', 2]
# 3 - **********************************(1+2)*3***********************************
# [1, '+', 2, '*', 3]
# 4 - ********************************sin(x)*x**2*********************************
# ['sin', 'x', '*', 'x', 'pow', 2]
# 5 - ***********************************cos(x)***********************************
# ['cos', 'x']
# 6 - *******************************True and False*******************************
# ['&&', True, False]
# 7 - ********************************sin(w*time)*********************************
# ['sin', 'w', '*', 'time']
我想了解如何將複雜綴數學表達式轉換爲後綴表達式被送到了一大口C包裝,要做到這一點,我試圖使用AST模塊。
任何人都可以在這裏建議嗎?
非常感謝你的回答,我沒有想過那個,很酷。當你說'如果你想要前綴符號只是交換命令,所以操作符/函數首先被訪問,你能否請詳細說明一下。',你是什麼意思? +1 – BPL
@BPL新增前綴表達式的例子,希望它有幫助! – niemmi
太棒了,謝謝 – BPL