Develop Reference

Struggling with how to iterate data

I am learning Python3 and I have a fairly simple task to complete but I am struggling how to glue it all together. I need to query an API and return the full list of applications which I can do and I store this and need to use it again to gather more data for each application from a different API call.
applistfull = requests.get(url,authmethod)
if applistfull.ok:
data = applistfull.json()
for app in data["_embedded"]["applications"]:
print(app["profile"]["name"],app["guid"])
summaryguid = app["guid"]
else:
print(applistfull.status_code)
I next have I think 'summaryguid' and I need to again query a different API and return a value that could exist many times for each application; in this case the compiler used to build the code.
I can statically call a GUID in the URL and return the correct information but I haven't yet figured out how to get it to do the below for all of the above and build a master list:
summary = requests.get(f"url{summaryguid}moreurl",authmethod)
if summary.ok:
fulldata = summary.json()
for appsummary in fulldata["static-analysis"]["modules"]["module"]:
print(appsummary["compiler"])
I would prefer to not yet have someone just type out the right answer but just drop a few hints and let me continue to work through it logically so I learn how to deal with what I assume is a common issue in the future. My thought right now is I need to move my second if up as part of my initial block and continue the logic in that space but I am stuck with that.

You are on the right track! Here is the hint: the second API request can be nested inside the loop that iterates through the list of applications in the first API call. By doing so, you can get the information you require by making the second API call for each application.

import requests
applistfull = requests.get("url", authmethod)
if applistfull.ok:
data = applistfull.json()
for app in data["_embedded"]["applications"]:
print(app["profile"]["name"],app["guid"])
summaryguid = app["guid"]
summary = requests.get(f"url/{summaryguid}/moreurl", authmethod)
fulldata = summary.json()
for appsummary in fulldata["static-analysis"]["modules"]["module"]:
print(app["profile"]["name"],appsummary["compiler"])
else:
print(applistfull.status_code)

Marking an email as read python

I'd like to mark an email as read from my python code. I'm using
from exchangelib import Credentials, Account
my_account = Account(...)
credentials = Credentials(...)
to get access to the account. This part works great. I then get into my desired folder using this
var1 = my_account.root / 'branch1' / 'desiredFolder'
Again, this works great. This is where marking it as read seems to not work.
item = var1.filter(is_read=False).values('body')
for i, body in enumerate(item):
#Code doing stuff
var1.filter(is_read=False)[i].is_read = True
var1.filter(is_read=False)[i].save(updated_fields=['is_read'])
I've tried the tips and answers from this post Mark email as read with exchangelib, but the emails still show as unread. What am I doing wrong?

I think you the last line of code that you save() do not work as you think that after you set is_read of unread[i] element to True, this unread[i] of course not appear in var1.filter(is_read=False)[i] again, so you acttually did not save this.
I think this will work.
for msg in my_account.inbox.filter(is_read=False):
msg.is_read = True
msg.save(updated_fields=['is_read'])

To expand on #thangnd's answer, the reason your code doesn't work is that you are calling .save() on a different Python object than the object you are setting the is_read flag on. Every time you call var1.filter(is_read=False)[i], a new query is sent to the server, and a new Python object is created.
Additionally, since you didn't specify a sort order (and new emails may be incoming while the code is running), you may not even be hitting the same email each time you call var1.filter(is_read=False)[i].

If statement does not work properly unless I use a debugger to step through it. Using pytube

I'm using pytube to convert a url that is for sure a link to a YouTube playlist into a pytube.Playlist()
if "/playlist?list=" in url:
playlist = Playlist(url)
if len(playlist.video_urls._elements) == 0:
print("Some error message")
The problem is that the playlist I'm using to test this has about 300 videos in it, so this if statement should be skipped, but instead, it goes into it and prints the error message. So naturally, I went to check it out with the debugger, and for some reason, once I start stepping into the code, it works the way it should and skips the if statement.
Anyone know what might be the problem?
IDE: Visual Studio Code
OS: Windows 10

Playlist.video_urls is a DeferredGeneratorList, not a list. So until you iterate over it, it doesn't have a length.
#property # type: ignore
#cache
def video_urls(self) -> DeferredGeneratorList:
"""Complete links of all the videos in playlist
:rtype: List[str]
:returns: List of video URLs
"""
return DeferredGeneratorList(self.url_generator())
Moreover, you're checking the length of _elements which is private to the class/API. And it's initialised to an empty list so it's length is always initially zero.
So either call len() on playlist.video_urls or better, use the provided method to populate the list generate_all() or just call list() on it.
The reason it works in your debugger is that the debugger tries to access the elements of the list to find its length, which triggers the iteration and populates it.
Good on you for at least trying the debugger and noticing the difference in behaviour for normal execution vs debugger execution! +1
And instead of checking the length, just iterate over it and check if anything was done, with a flag value:
if "/playlist?list=" in url:
playlist = Playlist(url)
had_videos = False # initial value
for video in playlist.video_urls:
had_videos = True # if exec gets here, you had at least one vid
# do something with each `video`
if not had_videos:
print("Some error message")

server name reachability in dnspython

I am currently trying to find a way to check whether or not the name servers can respond to either TCP or UDP packets.
My idea behind that was, to get all the name servers from a website (for example google.com), store them in a list, and then try to send TCP and UDP messages to all of them.
Although I am getting the name servers, my interpreter shows a problem when I am trying to make a query on udp(check udpPacket on the code) saying:
"TypeError: coercing to Unicode: need string or buffer, NS found"
I am new in Python(coming from C and C++) and I am guessing this is just incompatible types.
I checked dnspython's documentation and could not find what kind of type NS is (probably it's a type by itself) and why it cannot be passed as an argument.
What do you think the problem is? Is there maybe a better way to solve that kind of problem?
def getNSResults(url):
#create an empty list where we can store all the nameservers we found
nameServers = []
nameServers = dns.resolver.query(url,dns.rdatatype.NS, raise_on_no_answer=False)
#create a dictionary where based on all the nameservers.
#1st label refers to the ns name of our url that we inserted.
#2nd label shows wether or not we received a UDP response or not.
#3rd label shows wether or not we received a TCP response or not.
results = {}
for nameServer in nameServers:
#make a dns ns query, acts as a dumb message since whatever we send we just care of what we get back
query = dns.message.make_query(dns.name.from_text(url), dns.rdatatype.ANY)
query.flags |= dns.flags.AD
query.find_rrset(query.additional, dns.name.root, 65535, dns.rdatatype.OPT, create=True, force_unique=True)
#try sending a udp packet to see if it's listening on UDP
udpPacket = dns.query.udp(query,nameServer)
#try sending a tcp packet to see if it's listening on TCP
tcpPacket = dns.query.tcp(None,nameServer)
#add the results in a dictionary and return it, to be checked later by the user.
results.update({"nsName" == nameServer, "receivedUDPPacket" == isNotNone(udpPacket),"receivedTCPPacket" == isNotNone(tcpPacket)})
Thanks in advance!

Looking at your code, I see some DNS problems, some Python problems, and some dnspython problems. Let's see if we can't learn something together.
DNS
First, the parameter to your function getNSResults is called url. When you send DNS queries, you query for a domain name. A URL is something totally different (e.g. https://example.com/index.html). I would rename url to something like domain_name, domain, or name. For more on the difference between URLs and domain names, see https://www.copahost.com/blog/domain-vs-url/.
Second, let's talk about what you're trying to do.
i am currently trying to find a way to check wether or not the name servers can respond to either tcp or udp packets.
My idea behind that was, to get all the name servers from a website (for example google.com), store them in a list, and then, try to send tcp and udp messages to all of them.
That sounds like a great approach. I think you might be missing a few details here. so let me explain the steps you can take to do this:
Do an NS query for a domain name. You already have this step in your code. What you'll actually get from that query is just another domain name (or multiple domain names). For example, if you run dig +short NS google.com, you'll get this output:
ns3.google.com.
ns1.google.com.
ns4.google.com.
ns2.google.com.
At this step, we have a list of one or more names of authoritative servers. Now we need an IP address to use to send them queries. So we'll do a type A query for each of the names we got from step 1.
Now we have a list of IP addresses. We can send a DNS query over UDP and one over TCP to see if they're supported.
Python
For the most part, your Python syntax is okay.
The biggest red flag I see is the following code:
results.update({"nsName" == nameServer,
"receivedUDPPacket" == isNotNone(udpPacket),
"receivedTCPPacket" == isNotNone(tcpPacket)})
Let's break this down a bit.
First, you have results, which is a dict.
Then you have this:
{"nsName" == nameServer,
"receivedUDPPacket" == isNotNone(udpPacket),
"receivedTCPPacket" == isNotNone(tcpPacket)}
which is a set of bools.
What I think you meant to do was something like this:
results.update({
"nsName": nameServer,
"receivedUDPPacket": true,
"receivedTCPPacket": true
})
Function and variables names in Python are usually written in lowercase, with words separated by underscores (e.g. my_variable, def my_function()). Class names are usually upper camel case (e.g. class MyClass).
None of this is required, you can name your stuff however you want, plenty of super popular libraries and builtins break this convention, just figured I'd throw it out there because it can be helpful when reading Python code.
dnspython
When you're not sure about the types of things, or what attributes things have, remember these four friends, all builtin to Python:
1. pdb
2. dir
3. type
4. print
pdb is a Python debugger. Just import pdb, and the put pdb.set_trace() where you want to break. Your code will stop there, and then you can check out the values of all the variables.
dir will return the attributes and methods of whatever you pass to it. Example: print(dir(udpPacket)).
type will return the type of an object.
print as you probably already know, will print out stuff so you can see it.
I'm going to leave this part for you to test out.
Run dir() on everything if you don't know what it is.
I also should probably mention help(), which is super useful for built-in stuff.
The summary for this section is that sometimes documentation isn't all there, or hard to find, especially when you're new to a language/library/whatever.
So you have to figure stuff out on your own, and that means using all the tools I've just mentioned, looking at the source code, things like that.
Summary
I hope this was helpful. I know it's a lot, it's probably too much, but just be patient and know that DNS and Python are some very useful and fun things to learn about.
I went ahead and wrote something up that is a start at what I think you're hoping to achieve.
I recommend walking through the whole thing and making sure you understand what's going on.
If you don't understand something, remember pdb and dir (and there's always Google, SO, etc).
import dns.resolver
import dns.message
import dns.rdatatype
import json
import sys
def check_tcp_and_udp_support(name):
# this will give me the first default system resolver from /etc/resolv.conf
# (or Windows registry)
where = dns.resolver.Resolver().nameservers[0]
q = dns.message.make_query(name, dns.rdatatype.NS)
ns_response = dns.query.udp(q, where)
ns_names = [t.target.to_text() for ans in ns_response.answer for t in ans]
# this code is the same as the one-liner above
# ns_names = []
# for ans in ns_response.answer:
# for t in ans:
# ns_names.append(t.target.to_text())
results = {}
for ns_name in ns_names:
# do type A lookup for nameserver
q = dns.message.make_query(ns_name, dns.rdatatype.A)
response = dns.query.udp(q, where)
nameserver_ips = [item.address for ans in response.answer for item in ans.items if ans.rdtype == dns.rdatatype.A]
# now send queries to the nameserver IPs
for nameserver_ip in nameserver_ips:
q = dns.message.make_query('example.com.', dns.rdatatype.A)
try:
udp_response = dns.query.udp(q, nameserver_ip)
supports_udp = True
except dns.exception.Timeout:
supports_udp = False
try:
tcp_response = dns.query.tcp(q, nameserver_ip)
supports_tcp = True
except dns.exception.Timeout:
supports_tcp = True
results[nameserver_ip] = {
'supports_udp': supports_udp,
'supports_tcp': supports_tcp
}
return results
def main():
results = check_tcp_and_udp_support('google.com')
# this is just fancy JSON printing
# you could do print(results) instead
json.dump(results, sys.stdout, indent=4)
if __name__ == '__main__':
main()
Again, I hope this is helpful. It's hard when I don't know exactly what's going on in your head, but this is what I've got for you.

python requests...or something else... mysteriously caching? hashes don't change right when file does

I have a very odd bug. I'm writing some code in python3 to check a url for changes by comparing sha256 hashes. The relevant part of the code is as follows:
from requests import get
from hashlib import sha256
def fetch_and_hash(url):
file = get(url, stream=True)
f = file.raw.read()
hash = sha256()
hash.update(f)
return hash.hexdigest()
def check_url(target): # passed a dict containing hash from previous examination of url
t = deepcopy(target)
old_hash = t["hash"]
new_hash = fetch_and_hash(t["url"])
if old_hash == new_hash:
t["justchanged"] = False
return t
else:
t["justchanged"] = True
return handle_changes(t, new_hash) # records the changes
So I was testing this on an old webpage of mine. I ran the check, recorded the hash, and then changed the page. Then I re-ran it a few times, and the code above did not reflect a new hash (i.e., it followed the old_hash == new_hash branch).
Then I waited maybe 5 minutes and ran it again without changing the code at all except to add a couple of debugging calls to print(). And this time, it worked.
Naturally, my first thought was "huh, requests must be keeping a cache for a few seconds." But then I googled around and learned that requests doesn't cache.
Again, I changed no code except for print calls. You might not believe me. You might think "he must have changed something else." But I didn't! I can prove it! Here's the commit!
So what gives? Does anyone know why this is going on? If it matters, the webpage is hosted on a standard commercial hosting service, IIRC using Apache, and I'm on a lousy local phone company DSL connection---don't know if there are any serverside caching settings going on, but it's not on any kind of CDN.
So I'm trying to figure out whether there is some mysterious ISP cache thing going on, or I'm somehow misusing requests... the former I can handle; the latter I need to fix!