difficulty with Python

def myfunc(x):
 y = x
开发者_Go百科 y.append('How do I stop Python from modifying x here?')
 return y

x = []
z = myfunc(x)
print(x)

---

You do:

y = x[:]

to make a copy of list x.

---

You need to copy X before you modify it,

def myfunc(x):
 y = list(x)
 y.append('How do I stop Python from modifying x here?')
 return y

x = []
z = myfunc(x)
print(x)