在脚本中使用全局变量

Question

I threw the 'Apple-code' in the trash, please look at the following code :

# Define processing inputted line
def inputfile(line):
    linecontents = { 'item_0110':   line[0:8],
                     'item_0111':   line[8:16],
                     'item_0112':   line[16:24] }
    print 'In the function : ', linecontents
    print 'In the function : ', len(linecontents)

# Set dictionary
linecontents = {}

# Pretend to open a file and read line for line
line = '010012343710203053525150'

# Start processing the read line
inputfile(line)

# Display end resultprint
print '\nOutside the function : ', linecontents
print 'Outside the function : ', len(linecontents)

Ok, first off : I'm an idiot for trying this with vars. In the original post I already stated I have more than thirty items (fields if you want) in the file. To make matters more complex, a line from the file could look like this :

010012343710203053525150

And not all lines have the same fields so depending on what type of field it is, I would like to call a different function.

The question now is : why is the output like this :

In the function :  {'item_0112': '53525150', 'item_0111': '37102030', 'item_0110': '01001234'}
In the function :  3

Outside the function :  {}
Outside the function :  0

I thought the dictionary is independent from functions and/or classes ?

Answer 1

There are some issues with your code. I don't really see the see for global variables here.

I reformatted and refactored your code (no uppercase except for classes). You intent is not clear so I tried my best. The function read_file actually reads you file line by line and returns customer_name and customer_item line by line.

def read_file(filepath):
    with open(filepath) as customer_file:
        for line in customer_file:
            customer_name = line[:10]
            customer_item = line[10:]
            print('Name : ' + customer_name)
            print('Item : ' + customer_item)
            yield customer_name, customer_item

In the main() or whatever function, you can do what you want with the customer's variables.

What is important here, is that read_file actually reads a file and process the information for the file before returning them to the calling function.

def main():
    myfile = 'CustomerFile.txt'
    for customer_name, customer_item in read_file(myfile):
        if customer_item == 'Apple':
            print(customer_name)
        else:
            print(customer_name + ' is not eating an apple')

Answer 2

Instead of using globals, let the ReadFile function return the values

def ReadFile(line):
    ...
    return CustomerName, CustomerItem

and assign them to variables after calling the function:

for line in CustomerFile:
    CustomerName, CustomerItem = ReadFile(line)

---

def ReadFile(line):
    CustomerName = line[0:10]
    CustomerItem = line[10:]
    return CustomerName, CustomerItem

def Report(CustomerName, CustomerItem):   
    # Try to keep all print statements in one place
    print 'Name : ' + CustomerName
    print 'Item : ' + CustomerItem
    if CustomerItem == 'Apple':
        print CustomerName
    else:
        print CustomerName + ' is not eating an apple'

with open(CustomerFile.txt) as CustomerFile:
    for line in CustomerFile:
        CustomerName, CustomerItem = ReadFile(line)
        Report(CustomerName, CustomerItem)

---

Note that the PEP8 style guide recommends using lower_case for variable and function names and to reserve CamelCase for classes. While you are free to use your own style, use of PEP8 is quite prevalent and so by joining the PEP8-club your code will more naturally "fit in" with other people's code and vice-versa.

Answer 3

I found the (obvious) answer. As I said, my Python is a bit rusty :

## Define processing inputed line
#
def inputfile(line, linecontents):
    linecontents['item_0110'] = line[0:8]
    linecontents['item_0111'] = line[8:16]
    linecontents['item_0112'] = line[16:24]
    print 'In the function : ', linecontents
    print 'In the function : ', len(linecontents)

## Define main script
#
def main():
    # Set dict
    linecontents = {}

    # Pretend to open a file and read line for line
    line = '010012343710203053525150'

    # Start processing the read file
    inputfile(line, linecontents)

    # Display end resultprint
    print '\nOutside the funtion  : ', linecontents
    print 'Outsude the function : ', len(linecontents)


## Start main script
#
main()

And this neatly returns :

In the function :  {'item_0112': '53525150', 'item_0111': '37102030', 'item_0110': '01001234'}
In the function :  3

Outside the funtion  :  {'item_0112': '53525150', 'item_0111': '37102030', 'item_0110': '01001234'}
Outsude the function :  3