Cranky Frankie wrote:
> I'm reading in a pickled file. The program works but I'm having
> trouble sensing end of file. Here's the program:
>
> #
> # pickle_in.py
> # program to read in a pickled file
> #
> # Frank L. Palmeri
> #
>
> import pickle # import the pickle module
> pickle_file = open("d:/Work/pickle_file", "rb") # open the pickled input
> file
>
> read_file = pickle.load(pickle_file) # read the first input
> record
>
> new_list=[] # create a new empty list
>
> while pickle_file: # loop until end of file
> for i in range(0, 4): # iterate for each field
> new_list.append(read_file[i]) # append each field to
> the new list
> i = i + 1 # increment loop counter
> print(new_list) # print the input
> record from the new list
> new_list=[] # initialize the new
> list for the next record
> read_file = pickle.load(pickle_file) # read the next record
> in the input file
>
>
> here's the error:
>
> Traceback (most recent call last):
> File "D:\MyDocs\Python\pickle_in.py", line 21, in <module>
> read_file = pickle.load(pickle_file) # read the next record
> in the input file
> File "D:\Python31\lib\pickle.py", line 1365, in load
> encoding=encoding, errors=errors).load()
> EOFError
How did you write the data into the pickle file? The normal approach is to
write all your data in one step, e. g. (all code snippets untested)
# write list
with open(filename, "wb") as out:
pickle.dump(list_of_records, out)
You can then read back all records with
# read list
with open(filename, "rb") as instream:
list_of_records = pickle.load(instream)
A second approach is also possible, but not appropriate for a newbie:
# write list entries
with open(filename, "wb") as out:
for record in list_of_records:
pickle.dump(record, out)
# read list entries to rebuild the list
list_of_records = []
with open(filename, "rb") as instream:
while True:
try:
record = pickle.load(instream)
except EOFError:
break
else:
list_of_records.append(record)
By the way
> new_list=[]
> for i in range(0, 4):
> new_list.append(read_file[i])
> i = i + 1
- Here the for-loop is taking care of the value of i, you don't have to
increment it manually.
- A simpler way to achieve the same is
new_list = read_file[:4]
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