Passing a variable number of parameters in Python 3

Question

I would like to define a function that uses another function with a variable number of parameters passed as parameter. The problem is to get the parameters in (1) and pass them to the call in (2):

def f1(x):
  return x
def f2(x,a):
  return x+a  
def f3(x,a,b):
  return b*x+a

def genStr(x0,x1, n, f, *params):  # <----------------- (1)
  out = ''
  dx = (x1-x0)/(n-1)
  x = x0
  out += r'\draw[thick] '
  for k in range(0,n):
    if k!=0:
      out += r' -- '
    out += '({:.4f},{:.4f})'.format(x,f(x,params))  # <------- (2)
    x += dx
  out += r';'
  return out

print(genStr(0, 2, 3, f1))
print(genStr(0, 2, 3, f2, 0.1))
print(genStr(0, 2, 3, f3, 2, 0.3))

Patrick Artner · Accepted Answer · 2020-02-01 09:45:37Z

2

You need to unpack the params list:

out += '({:.4f},{:.4f})'.format(x,f(x, *params ))  # * == splat operator, unpacks list

to get

\draw[thick] (0.0000,0.0000) -- (1.0000,1.0000) -- (2.0000,2.0000);
\draw[thick] (0.0000,0.1000) -- (1.0000,1.1000) -- (2.0000,2.1000);
\draw[thick] (0.0000,2.0000) -- (1.0000,2.3000) -- (2.0000,2.6000);

answered Feb 1, 2020 at 9:45

Patrick Artner

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