Develop Reference

Instantiating classes with user input

I have just started learning about classes. In the examples that I'm learning I notice how everything that gets instantiated is hardcoded into the examples. I wanted to try and figure out if I could instantiate without having to do this, by means of user input.
In line 74/75 my expectation is that print(RecordID_map_PilotID[valUE].flownhours) prints me the number of hours I have chosen to log for a specific instance. Instead I'm confronted with the following pesky error:
Traceback (most recent call last):
File "oop_test.py", line 74, in <module>
RecordID_map_PilotID[valUE].recordflytime(loghours)
AttributeError: 'str' object has no attribute 'recordflytime'
Can anyone please help me understand why what I intend Python to do doesn't actually work?
Thank you!
PilotID_ClassValCalls = {}
RecordID_map_PilotID = {}
class PilotRecord:
department = "Aviation"
asset = "Employee"
assetcategory = "FTE"
flownhours = 0
def __init__(self, pilotid, name, age, licensestatus, licenseexpiration, shiptype, callsign, flownhours):
self.pilotid = pilotid
self.name = name
self.age = age
self.licensestatus = licensestatus
self.licenseexpiration = licenseexpiration
self.shiptype = shiptype
self.callsign = callsign
self.flownhours = flownhours
def __str__(self):
return f"{self.pilotid} has an {self.licensestatus} license with an expiration date of {self.licenseexpiration} with the following callsigns:\n {self.callsign} ."
def recordflytime(self, hours):
self.flownhours = self.flownhours + hours
def Adding_Pilot_Records(): #This definitions created new pilot records and instantiates a new object for each pilot rcord that is created. In addition memory values are stored in Dict
add_records_number = int(input("How many pilot records would you like to add? "))
for eachrecord in range(add_records_number):
record_store = [input("Please provide pilot ID: "), input("Please provide pilot Name: "), int(input("Please provide pilot Age: ")),
input("Please provide pilot licensestatus: "), input("Please provide pilot licenseexpiration: "), input("Please provide pilot shiptype: "), input("Please provide pilot callsign: "), 0]
PilotID_ClassValCalls.update({eachrecord + 1 : record_store[0]})
RecordID_map_PilotID.update({PilotID_ClassValCalls[eachrecord+1]: record_store[0]})
PilotID_ClassValCalls[eachrecord+1] = PilotRecord(record_store[0], record_store[1], record_store[2], record_store[3], record_store[4], record_store[5], record_store[6], record_store[7])
while True == True:
print("Hello, Welcome to the PILOT RECORD DATABASE\n",
"What would you like to do with the Records?:\n\n",
" \t1 - \"Add\"\n",
" \t2 - \"Log\"\n",
" \t3 - \"Delete\"\n",
" \t4 - \"Quit\"\n")
userchoice = str(input().lower().strip())
try:
if userchoice == "1" or userchoice == "add":
Adding_Pilot_Records()
continue
elif userchoice == "2" or userchoice == "log":
while userchoice == "2" or userchoice == "log":
pickarecord = str(input("Which Record ID would you like to create a log for? ")).split()
pickarecord_yesno = input(f"Selected Record >>> {RecordID_map_PilotID[pickarecord[0]]}, Is this the correct record? [Y] [N] [Quit]").upper().split()
userchoice = ""
if pickarecord_yesno[0] == "Q" or pickarecord_yesno[0] == "QUIT":
break
elif pickarecord_yesno[0] == "Y" or pickarecord_yesno[0] == "YES":
userchoice = ""
loghours = int(input(f"How many hours would you like to log?"))
pickarecord = str(pickarecord[0])
for record, valUE in RecordID_map_PilotID.items():
if pickarecord in valUE:
RecordID_map_PilotID[valUE].recordflytime(loghours)
print(RecordID_map_PilotID[valUE].flownhours)
elif pickarecord_yesno[0] == "N" or pickarecord_yesno == "NO":
userchoice = "2"
continue
elif userchoice == "3" or userchoice == "delete":
continue
elif userchoice == "4" or userchoice == "quit":
break
except ValueError:
print("Sorry an Error has occurred")

This is the line causing the error:
RecordID_map_PilotID[valUE].recordflytime(loghours)
You're trying to call .recordflytime() on RecordID_map_PilotID[valUE]. But RecordID_map_PilotID is a dictionary of type str -> str, so RecordID_map_PilotID[valUE] references a string and strings don't have .recordflytime() methods.
I can tell it's a string, because this line is the only line modifying it:
RecordID_map_PilotID.update({PilotID_ClassValCalls[eachrecord+1]: record_store[0]})
So, you're updating one dict with another, with a single key/value pair, the key being PilotID_ClassValCalls[eachrecord+1] and the value record_store[0]. PilotID_ClassValCalls is filled similarly, and its value also typically is record_store[0]. And you fill record store with the result of a call to input(), which is a string.
I would suggest you read some examples on object-oriented programming in Python - I think you're trying to do 'by hand' what is better done with the specific data structures and methods that exist for it in Python.
More generally, it's a good idea to separate the structures that hold and operate on data from the code that gets an processes input. After all, you want to manipulate these objects with direct user input now, but what if you save stuff out to a file and read it back later? Or perhaps call your code from a web page? You'd want to use the same classes, but without the direct calls to input() resulting in your code expecting input on the console.

validating input value but unable to try & except for other inputs too

i am trying to validate every input value but stuck here where if user put wrong value then my function stop taking other input & ask him to correct the error.
import re
import os.path
from csv import DictWriter
service ={}
class App:
def __init__(self):
pass
def services(self):
Problem is here
name=input("Enter Name: ")
name_r = re.match('^[a-zA-Z]{3,20}$',name)
if name_r:
print("true")
else:
print("Wrong Value Entered. Please Enter Correct Name")
i wanna use try & except block but exactly don't know how to use in this case.
if i put validated value in except block then rest of the input will also have have their own except block (am confused guide me) also the main problem, is there any short way to do this because if i validate each line like this so it will take so much time.
phone=input("Enter PTCL: ")
email=input("Enter Email: ")
mobile=input("Enter Mobile: ")
address=input("Enter Address: ")
service_type=input("Enter Problem Type: ")
date_time=input("Enter Date & Time: ")
msg=input("Enter Message: ")
Below Code is fine
#getting input values
service['name'] = name_r
service['ptcl'] = phone
service['mobile'] = mobile
service['date_time'] = date_time
service['service_type'] = service_type
service['address'] = address
service['msg'] = msg
service['email'] = email
file_exists = os.path.isfile(r"sevices.csv")
with open(r"sevices.csv",'a',newline='') as for_write:
writing_data = DictWriter(for_write,delimiter=',',fieldnames=["Name","Email","PTCL","Mobile","Service Type","Date & Time","Address","Message"])
if not file_exists:
writing_data.writeheader()
writing_data.writerow({
'Name': service['name'],
'Email':service['email'],
'PTCL':service['ptcl'],
'Mobile':service['mobile'],
'Service Type':service['service_type'],
'Date & Time':service['date_time'],
'Address':service['address'],
'Message':service['msg']
})
o1= App()
o1.services()

The easiest way to accomplish what you want is to create a while loop that exits on an accepted input.
while True:
name=input("Enter Name: ")
name_r = re.match('^[a-zA-Z]{3,20}$',name)
if name_r:
break
else:
print("Wrong Value Entered. Please Enter Correct Name")

Python 3.3 dump and load pickled dictionary

I am working through the chapter exercises in Tony Gaddis's "Starting Out With Python" 3rd edition from a class I have taken previously. I'm in chapter 9 and Exercise 8 requires me to write a program that pickles a dictionary (name:email) to a file when it closes and unpickles that file retaining the data when it is opened. I have read every word in that chapter and I still don't understand how you can do both in the same file. When you use the open function it creates a file which, in my understanding, is a new file with no data. I'm thinking it may be a sequencing issue, as in where to put the dump and load lines of code but that doesn't make sense either. Logic dictates you have to open the file before you can dump to it.
If the 'open' function creates a file object and associates it with a file and this function appears early in the code (as in def main), what keeps it from zeroing out the file each time that line is called?
This is not a homework assignment. I have completed that class. I am doing this for my own edification and would appreciate any explanation which would help me to understand it. I have included my attempt at the solution which is reflected in the code below and will keep gnawing at it until I find the solution. I just thought since the gene pool is deeper here I would save myself some time and frustration. Thank you very much to those that choose to reply and if I am lacking in any pertinent data that would help to clarify this issue, please let me know.
import pickle
#global constants for menu choices
ADDNEW = 1
LOOKUP = 2
CHANGE = 3
DELETE = 4
EXIT = 5
#create the main function
def main():
#open the previously saved file
friends_file = open('friends1.txt', 'rb')
#friends = pickle.load(friends_file)
end_of_file = False
while not end_of_file:
try:
friends = pickle.load(friends_file)
print(friends[name])
except EOFError:
end_of_file = True
friends_file.close()
#initialize variable for user's choice
choice = 0
while choice != EXIT:
choice = get_menu_choice() #get user's menu choice
#process the choice
if choice == LOOKUP:
lookup(friends)
elif choice == ADDNEW:
add(friends)
elif choice == CHANGE:
change(friends)
elif choice == DELETE:
delete(friends)
#menu choice function displays the menu and gets a validated choice from the user
def get_menu_choice():
print()
print('Friends and Their Email Addresses')
print('---------------------------------')
print('1. Add a new email')
print('2. Look up an email')
print('3. Change a email')
print('4. Delete a email')
print('5. Exit the program')
print()
#get the user's choice
choice = int(input('Enter your choice: '))
#validate the choice
while choice < ADDNEW or choice > EXIT:
choice = int(input('Enter a valid choice: '))
#return the user's choice
return choice
#the add function adds a new entry into the dictionary
def add(friends):
#open a file to write to
friends_file = open('friends1.txt', 'wb')
#loop to add data to dictionary
again = 'y'
while again.lower() == 'y':
#get a name and email
name = input('Enter a name: ')
email = input('Enter the email address: ')
#if the name does not exist add it
if name not in friends:
friends[name] = email
else:
print('That entry already exists')
print()
#add more names and emails
again = input('Enter another person? (y/n): ')
#save dictionary to a binary file
pickle.dump(friends, friends1.txt)
friends1.close()
#lookup function looks up a name in the dictionary
def lookup(friends):
#get a name to look up
name = input('Enter a name: ')
#look it up in the dictionary
print(friends.get(name, 'That name was not found.'))
#the change function changes an existing entry in the dictionary
def change(friends):
#get a name to look up
name = input('Enter a name: ')
if name in friends:
#get a new email
email = input('Enter the new email address: ')
#update the entry
friends[name] = email
else:
print('That name is not found.')
#delete an entry from the dictionary
def delete(friends):
#get a name to look up
name = input('Enter a name: ')
#if the name is found delete the entry
if name in friends:
del [name]
else:
print('That name is not found.')
#call the main function
main()

If you open a file for reading with open("my_file","r") it will not change the file. The file must already exist. If you open a file for writing with open("my_file","w") it will create a new file, overwriting the old one if it exists. The first form (reading) is the default so you can omit the second "r" argument if you want. This is documented in the Python standard library docs.

Use open("myfile", 'r+') this allows both read and write functions. (at least in 2.7)

How can I perform an action if a users input is the name of a file in a directory. Python

I am currently trying to make a program where the user can create sets of data, but I am having a difficult time figuring out how to handle the user picking the user picking a name out of a list of files to edit or view.
Here is how I display the files they can choose from. How can I easily allow them to choose any one of the available files without hardcoding each individual one?
available_files = os.listdir('./DSC_Saves/')
print(available_files)
user_input = input('File Name: ')
What I would like to avoid doing is the following:
if user_input == available_files[0]:
#do action
elif user_input == available_files[1]:
#do action 2
elif user_input == available_files[2]:
#do action 3

As mentioned, you can do this by using in on the list of available files as follows:
available_files = os.listdir('./DSC_Saves/')
print(available_files)
while True:
user_input = input('File name: ')
if user_input in available_files:
break
print("You have selected '{}'".format(user_input))
Alternatively, to make it easier to type, you could present the user with a numeric menu to choose from as follows:
available_files = os.listdir('./DSC_Saves/')
for index, file_name in enumerate(available_files, start=1):
print('{:2} {}'.format(index, file_name))
while True:
try:
user_input = int(input('Please select a file number: '))
if 1 <= user_input <= len(available_files):
selected_file = available_files[user_input-1]
break
except ValueError as e:
pass
print("You have selected '{}'".format(selected_file))
Both solutions will continue prompting until a valid file name has been entered.
So for example you could see the following output:
1 test1.txt
2 test2.txt
Please select a file number: 3
Please select a file number: 2
You have selected 'test2.txt'

Continuous results from a single function call

I am extremely new to Python, and to programming in general, so I decided to write some basic code to help me learn the ins and outs of it. I decided to try making a database editor, and have developed the following code:
name = []
rank = []
age = []
cmd = input("Please enter a command: ")
def recall(item): #Prints all of the information for an individual when given his/her name
if item in name:
index = name.index(item) #Finds the position of the given name
print(name[index] + ", " + rank[index] + ", " + age[index]) #prints the element of every list with the position of the name used as input
else:
print("Invalid input. Please enter a valid input.")
def operation(cmd):
while cmd != "end":
if cmd == "recall":
print(name)
item = input("Please enter an input: ")
recall(item)
elif cmd == "add":
new_name = input("Please enter a new name: ")
name.append(new_name)
new_rank = input("Please enter a new rank: ")
rank.append(new_rank)
new_age = input("Please input new age: ")
age.append(new_age)
recall(new_name)
else:
print("Please input a valid command.")
else:
input("Press enter to quit.")
operation(cmd)
I want to be able to call operation(cmd), and from it be able to call as many functions/perform as many actions as I want. Unfortunately, it just infinitely prints one of the outcomes instead of letting me put in multiple commands.
How can I change this function so that I can call operation(cmd) once, and call the other functions repeatedly? Or is there a better way to go about doing this? Please keep in mind I am a beginner and just trying to learn, not a developer.

Take a look at your code:
while cmd != "end":
if cmd == "recall":
If you call operation with anything than "end", "recall" or "add", the condition within while is True, the next if is also True, but the subsequent ifs are false. Therefore, the function executes the following block
else:
print("Please input a valid command.")
and the while loop continues to its next lap. Since cmd hasn't changed, the same process continues over and over again.

You have not put anything in your code to show where operator_1, operator_2, and operator_3 come from, though you have hinted that operator_3 comes from the commandline.
You need to have some code to get the next value for "operator_3". This might be from a list of parameters to function_3, in which case you would get:
def function_3(operator_3):
for loopvariable in operator_3:
if loopvariable == some_value_1:
#(and so forth, then:)
function_3(["this","that","something","something else"])
Or, you might get it from input (by default, the keyboard):
def function_3():
read_from_keyboard=raw_input("First command:")
while (read_from_keyboard != "end"):
if read_from_keyboard == some_value_1:
#(and so forth, then at the end of your while loop, read the next line)
read_from_keyboard = raw_input("Next command:")

The problem is you only check operator_3 once in function_3, the second time you ask the user for an operator, you don't store its value, which is why its only running with one condition.
def function_3(operator_3):
while operator_3 != "end":
if operator_3 == some_value_1
function_1(operator_1)
elif operator_3 == some_value_2
function_2
else:
print("Enter valid operator.") # Here, the value of the input is lost
The logic you are trying to implement is the following:
Ask the user for some input.
Call function_3 with this input.
If the input is not end, run either function_1 or function_2.
Start again from step 1
However, you are missing #4 above, where you are trying to restart the loop again.
To fix this, make sure you store the value entered by the user when you prompt them for an operator. To do that, use the input function if you are using Python3, or raw_input if you are using Python2. These functions prompt the user for some input and then return that input to your program:
def function_3(operator_3):
while operator_3 != 'end':
if operator_3 == some_value_1:
function_1(operator_3)
elif operator_3 == some_value_2:
function_2(operator_3)
else:
operator_3 = input('Enter valid operator: ')
operator_3 = input('Enter operator or "end" to quit: ')

looks like you are trying to get input from the user, but you never implemented it in function_3...
def function_3(from_user):
while (from_user != "end"):
from_user = raw_input("enter a command: ")
if from_user == some_value_1:
# etc...