對函數的返回感到困惑

Question

好的，我在第一個程序上遇到了麻煩。 如果您不看這兩個函數，那么我想要的是如果“ cur”值不在最小值和最大值之間，因為它將“目標”變量更改為“ 0”，因此我可以在程序中使用它。 。但這似乎不可行...我使用“ return”錯誤嗎？ 基本上，函數需要把target從1到0 ，這樣ri_fit變為0，讓我最后if thingys觸發...

對不起，代碼不好，我才剛剛開始！

#Clearance calculator
#clearances are in clearances.txt

targets = open("clearances.txt", "r")
lines = targets.readlines()   #get target clearances from file

in_min_target = float(lines[2])     #minimum intake clearance
in_max_target = float(lines[4])     #maximum intake clearance

ex_min_target = float(lines[8])    #miminum exhaust clearances
ex_max_target = float(lines[10])   #maximum exhaust clearances
targets.close

target_intake = (in_min_target + in_max_target) / 2     #find the ideal intake
target_exhaust = (ex_min_target + ex_max_target) / 2    #find the ideal exhaust

print "Intake Min: ", in_min_target
print "Intake Max: ", in_max_target
print "Exhaust Min: ", ex_min_target
print "Exhaust Max: ", ex_max_target
print """Target intake: %r
Target Exhaust: %r""" % (target_intake, target_exhaust)

print""
print "Enter current RIGHT side Intake clearance"
cur_r_in = float(raw_input(">"))
print ""
print "Enter current RIGHT side Exhaust clearance"
cur_r_ex = float(raw_input(">"))
print ""
print "Enter current LEFT side Intake clearance"
cur_l_in = float(raw_input(">"))
print ""
print "Enter current LEFT side Exhaust clearance"
cur_l_ex = float(raw_input(">"))


target = 1

def in_range(min, max, cur, valve, target):  #figures if intake valves are correct
    if min <= cur <= max:
        print "%r is in range." % valve
        target=1

    else:
        print "%r is OUT OF RANGE." %valve
        target=0

    return target

def ex_range(min, max, cur, valve, target):   #figures if exhaust valves are correct
    if min <= cur <= max:
        print "%r is in range." % valve
        target=1

    else:
        print "%r is OUT OF RANGE." %valve
        target=0
    return target


ri_fit = 1
re_fit = 1        #Assumes all valves are right, until further notice...
li_fit = 1
le_fit = 1

valve = "Right Intake"
print in_range(in_min_target, in_max_target, cur_r_in, valve, target)
print target
if target == 0:
    ri_fit = 0


print ""

valve = "Right Exhaust"
print ex_range(ex_min_target, ex_max_target, cur_r_ex, valve, target)

print ""

valve = "Left Intake"
print in_range(in_min_target, in_max_target, cur_l_in, valve, target)

print ""

valve = "Left Exhaust"
print ex_range(ex_min_target, ex_max_target, cur_l_ex, valve, target)

print ri_fit

if ri_fit==0:
    print "Right intake is out of range."
    print "Enter current right intake shim size."
    ri_cur_shim = int(raw_input(">"))

if re_fit==0:
    print "Right exhaust is out of range."
    print "Enter current right exhaust shim size."
    re_cur_shim = int(raw_input(">"))

if li_fit==0:
    print "Right intake is out of range."
    print "Enter current right intake shim size."
    li_cur_shim = int(raw_input(">"))

if le_fit==0:
    print "Right exhaust is out of range."
    print "Enter current right exhaust shim size."
    le_cur_shim = int(raw_input(">"))

Answer 1

在其中一個函數中分配給target時，您將在其中替換名為target的參數的值，而不接觸全局函數。 因此，如果要將函數分配給全局目標，則無法在函數中定義新目標。

但是，如果您不想更改函數，則可以使用return返回一個值的事實（由於打印了它，您似乎已經明白了）。 如果不是將其打印出來，而是將其分配給目標，那么您將在所需的位置獲得所需的值，並且無論最終將計算的值放在何處，函數都將起作用。

Answer 2

return從函數返回一個值。 您可以將結果存儲在變量中。

在您的代碼中，您嘗試將target作為參數傳遞，然后設置其值，但是由於整數是不可變的，因此您將無法在函數內更改target 。

就您而言，我會將您的代碼更改為以下形式：

def ex_range(min, max, cur, valve):  # You don't need `target` here
    if min <= cur <= max:
        print "%r is in range." % valve
        target=1

    else:
        print "%r is OUT OF RANGE." %valve
        target=0
    return target

target = ex_range(...)  # Store the results in a variable

更好的是，使用布爾值：

def ex_range(min, max, cur, valve):  # You don't need `target` here
    if min <= cur <= max:
        print "%r is in range." % valve
        return True

    else:
        print "%r is OUT OF RANGE." %valve
        return False

Answer 3

我認為問題在於您將target作為一種價值而不是作為參考傳遞。 在函數中，應刪除target參數，而應編寫：

def ex_range(min, max, cur, valve):
    global target
    # ...
    # rest of your code

這樣，解釋器會識別出您正在嘗試設置全局target變量，而不是本地實例。

否則，您可以執行以下操作：

def in_range(min, max, cur, valve):  #figures if intake valves are correct
    if min <= cur <= max:
        print "%r is in range." % valve
        return 1

    else:
        print "%r is OUT OF RANGE." %valve
        return 0

target = in_range(...) # fill in args
print target

請參閱此相關問題。

Answer 4

首先，我估計close后需要() ：

target.close()

第二： in_range和ex_range完全相同！

第三，無論如何都可以，因此可以正常運行：

in_range(1,10,7,'Right Intake',1)
in_range(1,10,17,'Right Intake',1)

輸出：

>>> 'Right Intake' is in range.
>>> 'Right Intake' is OUT OF RANGE.

因此，可能是您傳遞給函數的參數不正確 ！ 檢查您是否從文件中正確讀取了它們。

最后，避免將min ， max用作參數，因為它們是built-in Python函數。