在if語句中調用函數

Question

我試圖在 if 語句中調用函數，但它不起作用。 這是我使用 Python 的第一次嘗試。 我做錯了什么？

#!/usr/bin/python


menu = raw_input ("Hello, please choose form following options (1,2,3) and press enter:\n"
    "Option 1\n"
    "Option 2\n"
    "Option 3\n")

if menu == str("1"):
    savinginfile = raw_input ("Please, state your name: ")
    option1()
elif menu == str("2"):
    print ("Option 2")
elif menu == str("3"):
    print ("Option 3")

def option1():
    test = open ("test.txt", "rw")
    test.write(savinginfile)
    print ("Option 1 used")
    test.close()

Answer 1

建議您將savinginfile作為參數傳遞：

def option1(savinginfile):
    test = open ("test.txt", "rw")
    test.write(savinginfile)
    print ("Option 1 used")
    test.close()

您需要在調用之前定義option1 。 Python 從上到下解釋。

Answer 2

在嘗試調用它之前，您需要定義您的函數。 只需將def option1(): #and all that code below it放在 if 語句上方即可。

拋出太多全局變量也是不好的做法。 您不應該savinginfile現在這樣使用savinginfile —— 而是將它作為參數傳遞給函數，並讓函數在它自己的范圍內運行。 您需要將要使用的文件名傳遞給函數，然后才能使用savinginfile 。 試試吧：

def option1(whattosaveinfile):
  test = open("test.txt","a+") #probably better to use a with statement -- I'll comment below.
  test.write(whattosaveinfile) #note that you use the parameter name, not the var you pass to it
  print("Option 1 used")
  test.close()

#that with statement works better for file-like objects because it automatically
#catches and handles any errors that occur, leaving you with a closed object.
#it's also a little prettier :) Use it like this:
#
# with open("test.txt","a+") as f:
#   f.write(whattosaveinfile)
# print("Option 1 used")
#
#note that you didn't have to call f.close(), because the with block does that for you
#if you'd like to know more, look up the docs for contextlib

if menu == "1": #no reason to turn this to a string -- you've already defined it by such by enclosing it in quotes
  savinginfile = raw_input("Please state your name: ")
  option1(savinginfile) #putting the var in the parens will pass it to the function as a parameter.

elif menu == "2": #etc
#etc
#etc