Python Crash

Posted Oct 11, 2019 Updated Jan 23, 2024

By Grace L

15 min read

Python Crash
images
- ku example
  - filter() function
Python example

Python Crash

String

str.count( sub, start= 0, end=len(string) )

List

  
1.	list.append(obj): 在列表末尾添加新的对象
2.	list.count(obj): 统计某个元素在列表中出现的次数
3.	list.extend(seq): 在列表末尾一次性追加另一个序列中的多个值（用新列表扩展原来的列表）
4.	list.index(obj): 从列表中找出某个值第一个匹配项的索引位置
5.	list.insert(index, obj): 将对象插入列表
6.	list.pop([index=-1]): 移除列表中的一个元素（默认最后一个元素），并且返回该元素的值
7.	list.remove(obj): 移除列表中某个值的第一个匹配项
8.	list.reverse(): 反向列表中元素
9.	list.sort( key=None, reverse=False): 对原列表进行排序
10.	list.clear(): 清空列表
11.	list.copy(): 复制列表

# a list of numbers from 0 to 67:
for i in range(68)

# return values
list.sort()  =None
sorted(list) =list

# separate
inventory = ["shoes, 12, 29.99", "shirts, 20, 9.99", "sweatpants, 25, 15.00", "scarves, 13, 7.75"]
for item in inventory:
    a=item.split(", ")
    name=a[0]
    num=a[1]
    price=a[2]
    print("The store has {} {}, each for {} USD.".format(num,name,price))

dictionary

  
############### dictionary mechanics ###############

sports = {'baseball': 9, 'basketball': 4, 'soccer': 4, 'cricket': 2}
sports['hockey']=3
sport=list(sports.keys())


############### dictionary accumulation ###############
credits=0
for i in sports:
    credits+= sports[i]

str1 = "peter piper picked a peck of pickled peppers"
freq = {}                 # check frequency
for i in str1:
    if i not in freq:
        freq[i]=0
    freq[i]+=1
best_char=freq.keys()[0]         # check bigest value & key
best_value=freq[freq.keys()[0]]
for j in freq:
    if freq[j]>freq[freq.keys()[0]]:
        best_char=j
        best_value=freq[j]

Tuple

  
tuples_lst = [('Beijing', 'China', 2008), ('London', 'England', 2012), ('Rio', 'Brazil', 2016, 'Current'), ('Tokyo', 'Japan', 2020, 'Future')]
country=[]
for i,j in enumerate(tuples_lst):
    country.append(j[1])

# Tuple Unpacking
(variable names) = (values)

julia = "Julia", "Roberts", 1967, "Duplicity", 2009, "Actress", "Atlanta, Georgia"

name, surname, birth_year, movie, movie_year, profession, birth_place = julia
name, surname, birth_year, movie, movie_year, profession, birth_place="Julia", "Roberts", 1967, "Duplicity", 2009, "Actress", "Atlanta, Georgia"

print(name)   # julia

# variable names on the left side!!
# "Julia", "Roberts", 1967, "Duplicity", 2009, "Actress", "Atlanta, Georgia" = name, surname, birth_year, movie, movie_year, profession, birth_place
# SyntaxError: can't assign to literal on line 7

(a, b, c, d) = (1, 2, 3)  # ValueError: need more than 3 values to unpack
(a, b, c, d) = (1, 2, 3, 4)

students = [('Tommy', 95), ('Linda', 63), ('Carl', 70), ('Bob', 100), ('Raymond', 50), ('Sue', 75)]
passed = [ name for (name,grade) in students if grade>=70 ]

Sorted

  
letters = "alwnfiwaksuezlaeiajsdl"
sorted_letters=sorted(letters, reverse=True)

# according to the dic value
medals = {'Japan':41, 'Russia':56, 'South Korea':21, 'United States':121, 'Germany':42, 'China':70}
sort_list = sorted(medals, reverse=True, key=lambda key:medals[key])
top_three = sorted(medals, reverse=True, key=lambda key:medals[key])[:3]

# according second letter
list = ['hi', 'how are you', 'bye', 'BigBlueberry', 'zebra', 'dance']
lambda_sort=sorted(ex_lst, key=lambda str: str[1])


# case-insensitive string comparison:
sorted("This is a test string from Andrew".split(), key=str.lower)
# ['a', 'Andrew', 'from', 'is', 'string', 'test', 'This']



# Operator Module Functions
# Python provides convenience functions to make accessor functions easier and faster. The operator module has itemgetter(), attrgetter(), and a methodcaller() function.
from operator import itemgetter, attrgetter
class Student:
    def __init__(self, name, grade, age):
        self.name = name
        self.grade = grade
        self.age = age
    def __repr__(self):
        return repr((self.name, self.grade, self.age))
student_objects = [
    Student('john', 'A', 15),
    Student('jane', 'B', 12),
    Student('dave', 'B', 10),
]
# sort by age:
sorted(student_objects, key=lambda student: student.age)
# sort by age:
sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
# sort by grade then by age:
sorted(student_tuples, key=itemgetter(1,2))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]
# sort by age:
sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
# sort by grade then by age:
sorted(student_objects, key=attrgetter('grade', 'age'))
[('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)]


# Sort Stability and Complex Sorts
s = sorted(student_objects, key=attrgetter('age'))     # sort first on secondary key
sorted(s, key=attrgetter('grade'), reverse=True)       # now sort on primary key, descending
# [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
def multisort(xs, specs):
    for key, reverse in reversed(specs):
        xs.sort(key=attrgetter(key), reverse=reverse)
    return xs
multisort(list(student_objects), (('grade', True), ('age', False)))



# The Old Way Using Decorate-Sort-Undecorate¶
decorated = [(student.grade, i, student) for i, student in enumerate(student_objects)]
decorated.sort()
[student for grade, i, student in decorated]               # undecorate
[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]

Functions

  
def length(inlist):
    if len(inlist) >= 5:
        return "Longer than 5"
    else:
        return "Less than 5"

def test(x, abool = True, dict1 = {2:3, 4:5, 6:8}):
    return abool and dict1.get(x, False)
test(5, dict1 = {5:4, 2:1})


def strip_punctuation(string):   # move the punctuation
    for i in string:
        if i in ["'", '"', ",", ".", "!", ":", ";", '#', '@']:
            string=string.replace(i,'')
    return string

lambda

  
def fname(arguments):
    return value

fname = lambda arguments: value


mult = lambda int,x=6: int*x

greeting = lambda name, greeting="Hello ", excl="!": greeting + name + excl


lst_check = ['plums', 'watermelon', 'kiwi', 'strawberries', 'blueberries', 'peaches', 'BigBlueberry', 'mangos', 'papaya']
map_testing= map( lambda s: 'Fruit: '+s, lst_check)

countries = ['Canada', 'Mexico', 'Brazil', 'Chile', 'Denmark', 'Botswana', 'Spain', 'Britain', 'Portugal', 'Russia', 'Thailand', 'Bangladesh', 'Nigeria', 'Argentina', 'Belarus', 'Laos', 'Australia', 'Panama', 'Egypt', 'Morocco', 'Switzerland', 'Belgium']
b_countries= filter( lambda s: s[0]=='B' , countries)

def get_related_titles(lst):
    titlelst=[]
    for name in lst:
        [titlelst.append(name) for name in extract_movie_titles(get_movies_from_tastedive(name)) if name not in titlelst]
    return titlelst


sum = lambda arg1, arg2: arg1 + arg2
print ("sum= ", sum( 10, 20 ))
sum=30

together= lambda num,abc,x=" ":x.join([str(num),abc])

zip, map filter

  
l1 = ['left', 'up', 'front']
l2 = ['right', 'down', 'back']
zip(l1,l2) = [('left', 'right'), ('up', 'down'), ('front', 'back')]

opposites= [ (x1,x2) for (x1,x2) in zip(l1,l2) if len(x1)>3 and len(x2)>3 ]


def square(x) : return x ** 2
map(square, [1,2,3,4,5])
map(lambda x: x ** 2, [1, 2, 3, 4, 5])

filter(function, sequence)

lst_check = ['plums', 'watermelon', 'kiwi', 'strawberries', 'blueberries', 'peaches', 'BigBlueberry', 'mangos', 'papaya']
# elements in lst_check that have a w
filter_testing=list( filter( lambda value: 'w' in value, lst_check) )

test

  
assert sorted([1, 7, 4]) == [1, 4, 7]
assert sorted([1, 7, 4], reverse=True) == [7, 4, 1]

except

  
try:
    items = ['a', 'b']
    third = items[3]
    print("This won't print")
except Exception:
    print("got an error")


full_lst = ["ab", 'cde', 'fgh', 'i', 'jkml', 'nop', 'qr', 's', 'tv', 'wxy', 'z']
attempt = []

for elem in full_lst:
    try:
        attempt.append(elem[1])
    except:
        attempt.append("Error")

RegularExpression

  
# ^	Matches the beginning of a line
# $	Matches the end of the line
# .	Matches any character
# \s	Matches whitespace
# \S	Matches any non-whitespace character
# *	    Repeats a character zero or more times
# *?	Repeats a character zero or more times (non-greedy)
# +	    Repeats a character one or more times
# +?	Repeats a character one or more times (non-greedy)
# [aeiou]	Matches a single character in the listed set
# [^XYZ]	Matches a single character not in the listed set
# [a-z0-9]	The set of characters can include a range
# (	Indicates where string extraction is to start
# )	Indicates where string extraction is to end

import re

hand = open('file.txt')
    for line in hand:
        line = line.rstrip()
        if re.search('From:', line):
            print(line)


x='my 2 favoriate numbers are 19 and 42'
y=re.findall('[0-9]+',x)
print(y)     # ['2', '19', '42']


# greedy match
x='From: sing the : character.'
y=re.findall('^F.+:',x)   # greedy: it will give back the largest one.
print(y)                  # ['From: sing the : ']
y=re.findall('^F.+?:',x)  # dont be greedy: add '?'
print(y)                  # ['From:']

Data collect

  
import requests
import json

page = requests.get("https://api.datamuse.com/words?rel_rhy=funny")

print(type(page))       #<class 'requests.Response'>

print(page.text[:150])  # print the first 150 characters
#[{"word":"money","score":4417,"numSyllables":2},{"word":"honey","score":1208,"numSyllables":2},{"word":"sunny","score":720,"numSyllables":2},{"word":"

print(page.url)          # print the url that was fetched
#https://api.datamuse.com/words?rel_rhy=funny

x = page.json()            # turn page.text into a python object
x = jsno.loads(page, text) # list

------------------------------------

d = {'q': '"violins and guitars"', 'tbm': 'isch'}
results = requests.get("https://google.com/search", params=d)
results.url  # https://www.google.com/search?q=%22violins+and+guitars%22&tbm=isch
results.text

------------------------------------

import requests_with_caching
import json

parameters = {"term":"ann arbor", "entity": "podcast"}
response = requests_with_caching.get("https://api.datamuse.com/words?rel_rhy=happy", permanent_cache_file="data_cache.txt")

py_data = json.loads(data_cache.txt)
for r in py_data['results']:
    print(r['trackName'])

------------------------------------

import requests

def requestURL(baseurl, params = {}):
    # accepts a URL path and a params diction as inputs.
    # calls requests.get() with those inputs,
    # and returns the full URL of the data you want to get.
    req = requests.Request(method = 'GET', url = baseurl, params = params)
    prepped = req.prepare()
    return prepped.url

print(requestURL(some_base_url, some_params_dictionary))

https://api.datamuse.com/words?rel_rhy=funny

print(requestURL("https://api.datamuse.com/words", {"rel_rhy":"funny"}) )

Network with PY

  
# make a socket, a connection
import socket
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect( ('data.pr4e.org', 80))   # host and port

# HTTP
# https:// www.goo.com/ index.html
# protocol+host+document
import socket
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect( ('data.pr4e.org', 80))   # host and port
cmd = 'GET https://data.pr4e.org/romeo.txt HTTP/1.0\r\n\r\n'.encode()
mysock.send(cmd)

while True:
    data = mysock.recv(512)
    if (len(data) < 1):
        break
    print(data.decode())
mysock.close()

class

  
class Car:
    def __init__(self, make, model, year):
        self.make = make
        self.model = model self.year = year self.odometer_reading = 0

    def get_descriptive_name(self):
        long_name = f"{self.year} {self.manufacturer} {self.model}"
        return long_name.title()

    def read_odometer(self):
        print(f"This car has {self.odometer_reading} miles on it.")

    def update_odometer(self, mileage):
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage else:
            print("You can't roll back an odometer!")

    def increment_odometer(self, miles):
        self.odometer_reading += miles

class ElectricCar(Car):

    def __init__(self, make, model, year):
        super().__init__(make, model, year)
        self.battery_size = 75

    # Overriding Methods from the Parent Class
    def fill_gas_tank(self):
        print("This car doesn't need a gas tank!")

images

  
# face detect
import cv2 as cv
face_cascade = cv.CascadeClassifier('readonly/haarcascade_frontalface_default.xml')
eye_cascade = cv.CascadeClassifier('readonly/haarcascade_eye.xml')

img = cv.imread('readonly/floyd.jpg')

# convert it to grayscale using the cvtColor image
gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)

faces = face_cascade.detectMultiScale(gray)
# array([[158, 75, 176, 176]], dtype=int32)

faces = face_cascade.detectMultiScale(cv_img, 1.05)
show_rects(faces)


rec = faces.tolist()[0]
# [158, 75, 176, 176]


from PIL import Image
from PIL import ImageDraw


#  draw
pil_img=Image.fromarray(gray,mode="L")
drawing=ImageDraw.Draw(pil_img)
drawing.rectangle( (rec[0],rec[1], rec[0]+rec[2], rec[1]+rec[3]), outline="white")
display(pil_img)


pil_img = Image.open('readonly/msi_recruitment.gif')
pil_img.mode       # "P"


open_cv_version = pil_img.convert("L")
open_cv_version.save("msi_recruitment.png")


pil_img = pil_img.convert("RGB")
pil_img.mode       # "RBG"





# list all files in the current directory using os.listdir:
import os
for filename in os.listdir(os.getcwd()):
   with open(os.path.join(os.cwd(), filename), 'r') as f: # open in readonly mode
      # do your stuff

# list only some files, depending on the file pattern using the glob module:
import glob
for filename in glob.glob('*.txt'):
   with open(os.path.join(os.cwd(), filename), 'r') as f: # open in readonly mode
      # do your stuff

ku example

filter() function

filter out contents from a given sequence that can be a list, string or tuple etc.

filter(function, iterable)

Arguments:

An iterable sequence to be filtered.
a function that accepts an argument and returns bool
- i.e. True or False based on it’s logic.

Returns:

A new sequence of filtered contents.

Logic:

filter() iterates over all elements in the sequence and for each element it calls the given callback function.
If this function returns False then that element is skipped
returned True, elements are added into a new list.
In the end it returns a new list with filtered contents based on the function passed to it as argument.

  
def isOfLengthFour(strObj):
    if len(strObj) == 2:
        return True
    else:
        return False


# Filter a list of strings in Python using filter()
listOfStr = ['hi', 'this' , 'is', 'a', 'very', 'simple', 'string' , 'for', 'us']
filteredList = list(filter(isOfLengthFour , listOfStr))
# called isOfLengthFour() for each string element.
# filteredList:  ['hi', 'is', 'us']


filteredList = list(filter(lambda x : len(x) == 2 , listOfStr))
# filteredList:  ['hi', 'is', 'us']


strObj = 'Hi this is a sample string, a very sample string'
filteredChars = ''.join((filter(lambda x: x not in ['a', 's'], strObj)))
# Filtered Characters  :  Hi thi i  mple tring,  very mple tring


array1 = [1,3,4,5,21,33,45,66,77,88,99,5,3,32,55,66,77,22,3,4,5]
array2 = [5,3,66]
filteredArray = list(filter(lambda x : x not in array2, array1))
# Filtered Array  :  [1, 4, 21, 33, 45, 77, 88, 99, 32, 55, 77, 22, 4]

Python example

write

  
# writeDicToTXT
def writeDicToTXT(infodic, outfile):
    with open(outfile, 'w') as f:
        print(infodic, file=f)

# writeDicToCSV
import csv
my_dict={}
with open(filepath, 'w') as f:
    for key in my_dict.keys():
        f.write("%s,%s\n"%(key,my_dict[key]))

chop the api

  
import csv

def writeDicToTXT(infodic, outfile):
    with open(outfile, 'w') as f:
        print(infodic, file=f)

def createdic(apidic, apistr):
    stop = apistr.find("?")
    if stop == -1:
        apiname = apistr
    else:
        apiname = apistr[0:stop]
        value = apistr[stop:]

    if apiname not in apidic.keys():
        apidic[apiname] = []
#         print("api added: " + apiname)
#         print(apidic)
    value = apistr[stop:]
    while(1==1):
        valueH = 0
        valueT = value.find('=')
        vdata = value[valueH+1:valueT]
        vdata.strip()
        if(vdata not in apidic.get(apiname)):
            apidic.get(apiname).append(vdata)
#         print(vdata)
        if(value[valueT:].find('&') != -1):
            valueH = valueT + value[valueT:].find('&')
            value = value[valueH:]
        else:
            break
#     print(apidic)
    return apidic

# apistr="/xx/xx?xx=123&xxx=2347"
# apidic={}
# apidic=createdic(apidic, apistr)

def mfunc(path, infodic):
    with open(path) as csv_file:
        csv_reader = csv.reader(csv_file, delimiter=',')
        line_count = 0
        for row in csv_reader:
            if row != []:
                line_count += 1
                print(row)
                infodic = createdic(infodic, row[0])
    print(f'Processed {line_count} lines.')
    print(len(infodic))
    return infodic

sapidic={}
sapidic = mfunc('/Users/api.csv', sapidic)
print(len(sapidic))
writeDicToTXT(sapidic, "/Users/api.txt")

write dic to csv

logging

  
import sys
import logging
import os

logging.basicConfig(stream=sys.stdout, level=logging.INFO)
LOGGER = logging.getLogger(__name__)
LOGGER.setLevel(level=os.environ.get("LOG_LEVEL", "INFO").upper())

LOGGER.info("info()")

LOGGER.debug("debug")




from loguru import logger
logger.add(
    sys.stdout,
    backtrace=True, colorize=True,
    format="{time:YYYY-MM-DDTHH:mm:ss.SSS[Z]!UTC} - {level} - {file}:{line} - {message}")
logger.level("ERROR", color="<red>")

00CodeNote, PythonNote

Python

This post is licensed under CC BY 4.0 by the author.

Python Crash

String

List

dictionary

Tuple

Sorted

Functions

lambda

zip, map filter

test

except

RegularExpression

Data collect

Network with PY

class

images

ku example

filter() function

Python example

write

chop the api

write dic to csv

logging

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