We Keep Coding

How to separate user's input with two separators? And controlling the users input

I want to separate the users input using two different separators which are ":" and ";"
Like the user should input 4 subject and it's amounts. The format should be:
(Subject:amount;Subject:amount;Subject:amount;Subject:amount)
If the input is wrong it should print "Invalid Input "
Here's my code but I can only used one separator and how can I control the users input?
B = input("Enter 4 subjects and amount separated by (;) like Math:90;Science:80:").split(";")
Please help. I can't figure it out.

If you are fine with using regular expressions in python you could use the following code:
import re
output_list = re.split("[;:]", input_string)
Where inside the square brackets you include all the characters (also known as delimiters) that you want to split by, just make sure to keep the quotes around the square brackets as that makes a regex string (what we are using to tell the computer what to split)
Further reading on regex can be found here if you feel like it: https://medium.com/factory-mind/regex-tutorial-a-simple-cheatsheet-by-examples-649dc1c3f285
However, if you want to do it without importing anything you could do this, which is another possible solution (and I would recommend against, but it gets the job done well):
input_string = input_string.replace(";", ":")
output_list = input_string.split(":")
Which works by first replacing all of the semicolons in the input string with colons (it could also work the other way around) and then splitting by the remaining character (in this case the colons)
Hope this helped, as it is my first answer on Stack overflow.

Python writing into csv without line break \r\n

I am using Python 3 and scrapy to crawl some data. For some instances, I have 2 sentences which would like to write to excel as comma separated csv file.
How can I make them not to split into new line concernig the '\r\n'? Instead, how can I treat the whole sentence as a string
The sentences are as below
'USBについての質問です\r\n下記のサイトの通りCentOS7を１USBからインストールしよう...',
'USBからインストールしよう...',

Without seeing a code snippet of how you are parsing the strings, it's a bit difficult to suggest how exactly you can solve your problem. Anyway, you can always use replace to remove the occurrences of \r\n from your string:
>>> string = 'abc\r\ndef'
>>> print string
abc
def
>>> string.replace('\r\n', ' ')
'abc def'

Since you want to write to a CSV file, I'd suggest you use pandas dataframe as it make life whole lot a easier.
import pandas as pd
string="'USBについての質問です\r\n下記のサイトの通りCentOS7を１USBからインストールしよう...'\r\n'USBからインストールしよう...'"
string = string.repalce('\r\n',',')
list1=list(string)
df = pd.DataFrame(list1,columns=None,header=False)
df.to_csv('file.csv')

Thanks for all the advice and possible solution provided above. Yet, I have found the way to solve it.
string="'USBについての質問です\r\n下記のサイトの通りCentOS7を１USBからインストールしよう...'\r\n'USBからインストールしよう...'"
string.replace('\r','\\r').replace('\n','\\n'')
Then write this string into the csv will make the csv show \r\n together with the other text as a whole string.

How to read csv lines with pandas containing " and ' between quoting character "?

I'm trying to import csv with pandas read_csv and can't get the lines containing the following snippet to work:
"","",""BSF" code - Intermittant, see notes",""
I am able to get pass it via with the options error_bad_lines=False, low_memory=False, engine='c'. However it should be possible to parse them correctly. I'm not good with regular expressions so I didn't try using engine='python', sep=regex yet. Thanks for any help.

Well, that's quite a hard one ... given that all fields are quoted you could use a regex to only use , followed and preceded by " as a separator:
data = pd.read_csv(filename,sep=r'(?<="),(?=")',quotechar='"')
However, you will still end up with quotes around all fields, but you could fix this by applying
data = data.applymap(lambda s:s[1:-1])

Parsing a file in python

Caveat emptor: I can spell p-y-t-h-o-n and that's pretty much all there is to my knowledge. I tried to take some online classes but after about 20 lectures learning not much, I gave up long time ago. So, what I am going to ask is very simple but I need help:
I have a file with the following structure:
object_name_here:
object_owner:
- me#my.email.com
- user#another.email.com
object_id: some_string_here
identification: some_other_string_here
And this block repeats itself hundreds of times in the same file.
Other than object_name_here being unique and required, all other lines may or may not be present, email addresses can be from none to 10+ different email addresses.
what I want to do is to export this information into a flat file, likes of /etc/passwd, with a twist
for instance, I want the block above to yield a line like this:
object_name_here:object_owner=me#my_email.com,user#another.email.com:objectid=some_string_here:identification=some_other_string_here
again, the number of fields or length of the content fields are not fixed by any means. I am sure this is pretty easy task to accomplish with python but how, I don't know. I don't even know where to start from.
Final Edit: Okay, I am able to write a shell script (bash, ksh etc.) to parse the information, but, when I asked this question originally, I was under the impression that, python had a simpler way of handling uniform or semi-uniform data structures as this one. My understanding was proven to be not very accurate. Sorry for wasting your time.

As jaypb points out, regular expressions are a good idea here. If you're interested in some python 101, I'll give you some simple code to get you started on your own solution.
The following code is a quick and dirty way to lump every six lines of a file into one line of a new file:
# open some files to read and write
oldfile = open("oldfilename","r")
newfile = open("newfilename","w")
# initiate variables and iterate over the input file
count = 0
outputLine = ""
for line in oldfile:
# we're going to append lines in the file to the variable outputLine
# file.readline() will return one line of a file as a string
# str.strip() will remove whitespace at the beginning and end of a string
outputLine = outputLine + oldfile.readline().strip()
# you know your interesting stuff is six lines long, so
# reset the output string and write it to file every six lines
if count%6 == 0:
newfile.write(outputLine + "\n")
outputLine = ""
# increment the counter
count = count + 1
# clean up
oldfile.close()
newfile.close()
This isn't exactly what you want to do but it gets you close. For instance, if you want to get rid of " - " from the beginning of the email addresses and replace it with "=", instead of just appending to outputLine you'd do something like
if some condition:
outputLine = outputLine + '=' + oldfile.readline()[3:]
that last bit is a python slice, [3:] means "give me everything after the third element," and it works for things like strings or lists.
That'll get you started. Use google and the python docs (for instance, googling "python strip" takes you to the built-in types page for python 2.7.10) to understand every line above, then change things around to get what you need.

Since you are replacing text substrings with different text substrings, this is a pretty natural place to use regular expressions.
Python, fortunately, has an excellent regular expressions library called re.
You will probably want to heavily utilize
re.sub(pattern, repl, string)
Look at the documentation here:
https://docs.python.org/3/library/re.html
Update: Here's an example of how to use the regular expression library:
#!/usr/bin/env python
import re
body = None
with open("sample.txt") as f:
body = f.read()
# Replace emails followed by other emails
body = re.sub(" * - ([a-zA-Z.#]*)\n * -", r"\1,", body)
# Replace declarations of object properties
body = re.sub(" +([a-zA-Z_]*): *[\n]*", r"\1=", body)
# Strip newlines
body = re.sub(":?\n", ":", body)
print (body)
Example output:
$ python example.py
object_name_here:object_owner=me#my.email.com, user#another.email.com:object_id=some_string_here:identification=some_other_string_here

Reading and correctly understanding/interpreting control characters from a file (python)

I'm a python beginner and just ran into a simple problem: I have a list of names (designators) and then a very simple code that reads lines in a csv file and prints the csv lines that has a name in the first column (row[0]) in common with my "designator list". So:
import csv
DesignatorList = ["AAX-435", "AAX-961", "HHX-9387", "HHX-58", "K-58", "K-14", "K-78524"]
with open('DesignatorFile.csv','rb') as FileReader:
for row in csv.reader(FileReader, delimiter=';'):
if row[0] in DesignatorList:
print row
My csv files is only a list of names, like this:
AAX-435
AAX-961
HHX-58
HHX-9387
I would like to be able to use wildcards like * and ., example: let's say that I put this on my csv file:
AAX*
H.X-9387
*58
I need my code to be able to interpret those wild cards/control characters, printing the following:
every line that starts with "AAX";
every line that starts with "H", then any following character, then finally ends with "X-9387";
every line that ends with "58".
Thank you!
EDIT: For future reference (in case somebody runs into the same problem), this is how I solved my problem following Roman advice:
import csv
import re
DesignatorList = ["AAX-435", "AAX-961", "HHX-9387", "HHX-58", "K-58", "K-14", "K-78524"]
with open('DesignatorFile.txt','rb') as FileReader:
for row in csv.reader(FileReader, delimiter=';'):
designator_col0 = row[0]
designator_col0_re = re.compile("^" + ".*".join(re.escape(i) for i in designator_col0.split("*")) + "$")
for d in DesignatorList:
if designator_col0_re.match(d):
print d

Try the re module.
You may need to prepare regular expression (regex) for use by replacing '*' with '.*' and adding ^ (beginning of a string) and $ (end of string) to the beginning and the end of the regular expression. In addition, you may need to escape everything else by re.escape function (that is, function escape from module re).
In case you do not have any other "control characters" (as you call them), splitting the string by "*" and joining by ".*" after applying escape.
For example,
import re
def make_rule(rule): # where rule for example "H*X-9387"
return re.compile("^" + ".*".join(re.escape(i) for i in rule.split("*")) + "$")
Then you can match (I guess, your rule is row):
...
rule_re = make_rule(row)
for d in DesignatorList:
if rule_re.match(d):
print row # or maybe print d
(I have understood, that rules are coming from CSV file while designators are from a list. It's easy to do it the other way around).
The examples above are examples. You still need to adapt them into your program.

Python's string object does have a startswith and an endswith method, which you could use here if you only had a small number of rules. The most general way to go with this, since you seem to have fairly simple patterns, is regular expressions. That way you can encode those rules as patterns.
import re
rules = ['^AAX.*$', # starts with AAX
'^H.*X-9387$', # starts with H, ends with X-9387
'^.*58$'] # ends with 58
for line in reader:
if any(re.match(rule, line) for rule in rules):
print line