x is not defined, and you cannot pass f(x) in the parameter. Try doing something like this:

def f(x):
return x**2 + x - 5

def derivative(f,x,h):
return 1/(2*h) * (f(x+h) - f(x-h))

x=12345

print derivative(f,x,6)

When doing global price_buy that means you use the globally defined price_buy to be defined localy in your method but

• neither price_buy nor number_exit are defined globally (outside a method)
• you don't need global variable

They only to be local, and just better : inlined

def fun_price_buy():
    price_buy = np.random.randint(50000,300000)
    return price_buy

# inline, no temporaty variable is needed
def fun_price_buy():
    return np.random.randint(50000,300000)

Finally, and if you want to get the value from the method in a variable for doing something with it:

import numpy as np

# This function generates a list of numbers under certain rules
def num_var_list(number_exit):
    number_list = []
    number_target = number_exit
    num_max_robot = (number_target * 20) / 100
    while num_max_robot > 0:
        num_robot = np.random.randint(1,int(num_max_robot))
        if num_robot > number_target:
                number_list.append(number_target)
        else: 
            number_list.append(num_robot)
        number_target = number_target - number_target
    return number_list
        
def fun_price_buy():
    return np.random.randint(50000,300000)

def fun_mx_buy():
    return np.random.randint(50, 150)

lista_number_list = []
lista_price_buy = []
lista_mx_buy = []

# This loop append each function 50 times to a new list
while len(lista_price_buy) <= 50: 
    number_exit = fun_mx_buy()
    price_buy = fun_price_buy()
    vr_list = num_var_list(number_exit)
   
    lista_number_list.append(vr_list)
    lista_price_buy.append(price_buy )
    lista_mx_buy.append(number_exit )

The problem is that in your function, your asking the user to add a variable that will be the gender. However, the variable you give, gender, is not defined. Therefore, it raises an error.

To fix it, remove the parameters from the function, like this:

def clear_line():
    print("\n")

def id_check():
                    
    id = input(" Do you have an id? : ")    


    if (id == "yes" ) or (id == "Yes") or (id == "y"):
        
        id = True   
    
    elif (id == "no" ) or (id == "No") or (id == "n"):
        
        print ("I need your id")
                
    else:
        print ("Please respound with yes or no "), 
        clear_line()
        id_check(id)

    gender = input(" What is you gender ? ")
    print (gender)

id_check() 

Global in the context you put does not work across modules... if you did something like this, however, it would work

globvar = 0

def set_globvar_to_one():
    global globvar    # Needed to modify global copy of globvar
    globvar = 1

def print_globvar():
    print globvar     # No need for global declaration to read value of globvar

set_globvar_to_one()
print_globvar()       # Prints 1

see more here