「海峽」對象不是可調用，功能ARGS

Question

我試圖寫一個程序作爲一個練習從計算積分值與2個數學函數一個爲b。我的函數集成應該有作爲數學函數的集成。

from math import * 

def g(x): 
     return float(x) * float(x) + 3 

def h(x): 
    return math.cos(float(x) * float(x)) 

def integrate(f, a, b, n): 
    H = (abs(float(a) - float(b)))/float(n) 
    ans = 0 
    xWaarde = a - H/2 
    print xWaarde 
    for k in range(1, n+1): 
     xWaarde = xWaarde + H 
     ans = ans + f(xWaarde) * H 
    return ans 

print 'available functions:' 
print 'g(x) = x^2+3' 
while True: 
    print 'h(x) = cos(x^2)' 
    aIn = float(raw_input('integral from a = ')) 
    bIn = float(raw_input('to b = ')) 
    nIn = int(raw_input('Number of subintervals: ')) 
    while True: 
     funcIn = raw_input('Which function do you want to use? (g or h): ') 
     if funcIn == 'g': 
      integrate(g,aIn,bIn,nIn) 
      break 
     elif funcIn == 'h': 
      integrate(h,aIn,bIn,nIn) 
      break 
     else: 
      print 'This function is not available' 


    print 'The definite integral is', integrate(funcIn, aIn, bIn, nIn) 
    doorg = raw_input('Do you want to continue? (y or n): ') 
    if doorg == 'n': 
     break 
    else: 
     print 

完整回溯如下：

Traceback (most recent call last): 
    File "C:/Users/Nick van Stijn/Desktop/Python/Assignment 3.1.py", line 38, in <module> 
    print 'The definite integral is', integrate(funcIn, aIn, bIn, nIn) 
    File "C:/Users/Nick van Stijn/Desktop/Python/Assignment 3.1.py", line 16, in integrate 
    ans = ans + f(xWaarde) * H 
TypeError: 'str' object is not callable 

編輯：解決 我通過一次我沒有在所有調用它調用一個函數犯了一個錯誤。

Answer 1

的問題是，你使用正確的功能，f或g致電integrate，但隨後丟棄的結果，而不是調用integrate再次的打印，此時路過只是名稱的功能的， funcIn。

相反，你應該只把結果保存在一個變量，例如，像這樣：

result = None 
while result is None: 
    funcIn = raw_input('Which function do you want to use? (g or h): ') 
    if funcIn == 'g': 
     result = integrate(g,aIn,bIn,nIn) 
    elif funcIn == 'h': 
     result = integrate(h,aIn,bIn,nIn) 
    else: 
     print 'This function is not available' 

print 'The definite integral is', result 

此外，您還可以使用dict使用可能大量的函數名，以實際的功能映射，而不是的if/elif/else：

functions = {'h': h, 'g': g} 
while result is None: 
    funcIn = raw_input('Which function do you want to use? (g or h): ') 
    if funcIn in functions: 
     result = integrate(functions[funcIn],aIn,bIn,nIn) 
    else: 
     print 'This function is not available' 

Answer 2

你正在一個字符串的形式使用功能的文本名稱，而不是函數對象本身的引用。儘管從字符串名稱派生函數對象的方法很棘手，但它們很難維護並且容易出錯。由於python函數中的對象與其他任何對象（所謂的「第一類」對象）不同，因此它們並沒有真正的名稱，只有引用才能使函數具有名稱。

這是一本字典就派上用場了，特別是如果你想在以後添加更多功能的一個很好的例子。我們可以映射文本鍵（用戶輸入的）任何Python對象，其中一個功能：

from math import * 

def g(x): 
     return float(x) * float(x) + 3 

def h(x): 
    return math.cos(float(x) * float(x)) 

# Store references to the functions in a dictionary 
# with the keys as the text name (the names need not match) 
funcs = {'g': g, 'h': h}  # <<<< ADDED 

def integrate(f, a, b, n): 
    H = (abs(float(a) - float(b)))/float(n) 
    ans = 0 
    xWaarde = a - H/2 
    print xWaarde 
    for k in range(1, n+1): 
     xWaarde = xWaarde + H 
     ans = ans + f(xWaarde) * H 
    return ans 

print 'available functions:' 
print 'g(x) = x^2+3' 
while True: 
    print 'h(x) = cos(x^2)' 
    aIn = float(raw_input('integral from a = ')) 
    bIn = float(raw_input('to b = ')) 
    nIn = int(raw_input('Number of subintervals: ')) 
    while True: 
     funcIn = raw_input('Which function do you want to use? (g or h): ') 

     # THIS CODE CHANGED - note the simplification 
     # we just test for membership of the dictionary 
     if funcIn in funcs: 
      integrate(funcs[funcIn],aIn,bIn,nIn) 
      break 
     else: 
      print 'This function is not available' 

    # THIS CODE CHANGED (note first argument to integrate) 
    print 'The definite integral is', integrate(funcs[funcIn], aIn, bIn, nIn) 
    doorg = raw_input('Do you want to continue? (y or n): ') 
    if doorg == 'n': 
     break 
    else: 
     print