improving speed of Python module import

Not an actual answer to the question, but a hint on how to profile the import speed with Python 3.7 and tuna (a small project of mine):

python3 -X importtime -c "import scipy" 2> scipy.log
tuna scipy.log

You can import your modules manually instead, using imp. See documentation here.

For example, import numpy as np could probably be written as

import imp
np = imp.load_module("numpy",None,"/usr/lib/python2.7/dist-packages/numpy",('','',5))

This will spare python from browsing your entire sys.path to find the desired packages.

See also:

Manually importing gtk fails: module not found

You can use lazy imports, but it depends on your use case.

If it's an application, you can run necessary modules for GUI, then after window is loaded, you can import all your modules.

If it's a module and user do not use all the dependencies, you can import inside function.

[warning] It's against pep8 i think and it's not recomennded at some places, but all the reason behind this is mostly readability (i may be wrong though...) and some builders (e.g. pyinstaller) bundling (which can be solved with adding missing dependencies param to spec)

If you use lazy imports, use comments so user knows that there are extra dependencies.

Example:

import numpy as np

# Lazy imports
# import matplotlib.pyplot as plt

def plot():
    import matplotlib.pyplot as plt
    
    # Your function here
    # This will be imported during runtime 

For some specific libraries i think it's necessity.

You can also create some let's call it api in __init__.py

For example on scikit learn. If you import sklearn and then call some model, it's not found and raise error. You need to be more specific then and import directly submodule. Though it can be unconvenient for users, it's imho good practice and can reduce import times significantly.

Usually 10% of imported libraries cost 90% of import time. Very simple tool for analysis is line_profiler

import line_profiler
import atexit

profile = line_profiler.LineProfiler()
atexit.register(profile.print_stats)

@profile
def profiled_function():

    import numpy as np
    import pandas as pd
    import matplotlib.pyplot as plt


profiled_function()

This give results

Line #      Hits         Time  Per Hit   % Time  Line Contents
==============================================================
    20                                               @profile
    21                                               def profiled_function():
    22
    23         1    2351852.0 2351852.0      6.5          import numpy as np
    24         1    6545679.0 6545679.0     18.0          import pandas as pd
    25         1   27485437.0 27485437.0     75.5          import matplotlib.pyplot as plt

75% of three libraries imports time is matplotlib (this does not mean that it's bad written, it just needs a lot of stuff for grafic output)

Note:

If you import library in one module, other imports cost nothing, it's globally shared...

Another note:

If using imports directly from python (e.g pathlib, subprocess etc.) do not use lazy load, python modules import times are close to zero and don't need to be optimized from my experience...

1.35 seconds isn't long, but I suppose if you're used to half that for a "quick check" then perhaps it seems so.

Andrea suggests a simple client/server setup, but it seems to me that you could just as easily call a very slight modification of your script and keep it's console window open while you work:

• Call the script, which does the imports then waits for input
• Minimize the console window, switch to your work, whatever: *Do work*
• Select the console again
• Provide the script with some sort of input
• Receive the results with no import overhead
• Switch away from the script again while it happily awaits input

I assume your script is identical every time, ie you don't need to give it image stack location or any particular commands each time (but these are easy to do as well!).

Example RAAC's_Script.py:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import scipy.ndimage
import scipy.signal
import sys
import os

print('********* RAAC\'s Script Now Running *********')

while True: # Loops forever
    # Display a message and wait for user to enter text followed by enter key.
    # In this case, we're not expecting any text at all and if there is any it's ignored
    input('Press Enter to test image stack...')

    '''
    *
    *
    **RAAC's Code Goes Here** (Make sure it's indented/inside the while loop!)
    *
    *
    '''

To end the script, close the console window or press ctrl+c.

I've made this as simple as possible, but it would require very little extra to handle things like quitting nicely, doing slightly different things based on input, etc.

I have done just a basic test below, but it shows that runpy can be used to solve this issue when you need to have a whole Python script to be faster (you don't want to put any logic in test_server.py).

test_server.py

import socket
import time
import runpy
import matplotlib.pyplot

HOST = 'localhost'
PORT = 50007

serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
    serversocket.bind((HOST, PORT))
except:
    print("Server is already running")
    exit(1)

# Start server with maximum 100 connections
serversocket.listen(100)

while True:
    connection, address = serversocket.accept()
    buf = connection.recv(64)
    if len(buf) > 0:
        buf_str = str(buf.decode("utf-8"))
        now = time.time()
        runpy.run_path(path_name=buf_str)
        after = time.time()
        duration = after - now
        print("I received " + buf_str + " script and it took " + str(duration) + " seconds to execute it")

test_client.py

import socket
import sys

HOST = 'localhost'
PORT = 50007

clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
clientsocket.connect((HOST, PORT))

message = sys.argv[1].encode()

clientsocket.send(message)

test_lag.py

import matplotlib.pyplot

Testing:

$ python3 test_client.py test_lag.py
I received test_lag.py script and it took 0.0002799034118652344 seconds to execute it

$ time python3 test_lag.py

real    0m0.624s
user    0m1.307s
sys     0m0.180s

Based on this, module is pre-loaded for fast usage.

I think using threading wouldnot be really a bad idea

from concurrent.futures import ThreadPoolExecutor
imports = [
    "import numpy as np",
    "import matplotlib.pyplot as plt",
    "import matplotlib.animation as animation",
    "import scipy.ndimage",
    "import scipy.signal",
    "import sys",
    "import os",
]
def importModule(statement):
    try:
        exec(statement, globals())
    except Exception as e:
        print(f"Error importing {statement}: {e}")
with ThreadPoolExecutor(max_workers=len(imports)) as executor:
    futures = {executor.submit(importModule, statement): statement for statement in imports}
    for future in futures:
        future.result()