tags: python

python

print

• or
  It only print B if A is false or NULL
  print

  • print (0 or 1) ## 1
  • print(Flase or "hey") ##'hey'
  • print('hi'or'hey) ##'hi'
  • print([ ] or False) ## 'False'
  • print(False or [ ]) ## []

• and
  and only evalute the second argument if the first one is true

  • print(0 and 1) ## 0
  • print(1 and 0) ## 0
  • print(False and 'Hey') ##False
  • print('Hi' and 'Hey') ## 'Hey'
  • print([ ] and False) ##[ ]
  • print(False and [ ]) ## False

• operators

  • & performs binary AND
  • | performs binary or
  • ^ Performs a binary XOR operation
  • ~ performs a binary NOT operation
  • << shift left operation
  • ">> shift right operation

• other operator

  • is

  • in

• Ternay operator

  • use to define conditional

  def is_adult(age)
  if age >18:
  return True
  else:
  return False
  def is_adult2(age)
  return True if age>18 else False

• print with different line

  • 三個"可以做成很多行的輸出(若第一行的"後面沒接東西，就會變成多一行空格)

  • print("""Beau is

    39

    years old.
    """)

    輸出
    Beau is

    39

    years old.

• string modify
  上述這些都只是輸出當下改變的string。但本身的string值是不變的。

  • isalpha()
    去確定string裡面只有charactres 且不是空的
  • isalnum()
    確定string裡面只有character跟digits 且不是空的
  • isdecimal()
    確定string 裡面只有數字且不是空的
  • print("BEAU".lower())

  beau

  • print("beau".upper())

  BEAU

  • print('bEAu person'.title())
    it make first leeter of each string become capital letter

  Beau Person

  • print("Beau person".islower())

    False

  • print("person".islower())

    True
    is lower 是用來確定整個string是否都是小寫

  • startsswith()
    to check if the string starts with a specific substring
  • endswith()
    to check if the string ends with a specific substring
  • replace()
    to replace a part of a string
  • split()
    to split a string on a specific charactr separator
  • strip()
    to trim the whitespace from a string
  • join ()
    to append new letters to a string
  • find ()
    to find the postion of a substring

• global function

  • print(len(name))

    4

  • name ="beau"
    print("au" in name)

    True

  • name ="Be"au"
    print(name)

    BE"au
    \這個可以讓後面的"不再表示成本來的樣子，而是一般的string

  • name = 'Be"au'
    print(name)

    Be"au

  • name ='Be"'au'
    print(name)

    Be"'au

  • name = 'Be\nau'
    print(name)

    Be
    au

  • name ='Be\au'
    print(name)

    Beu

  • name = 'Be\au'
    print(name)

    Be\au

  • name ="Beau"
    print(name[1:2])
    從1開始回值，2之前的全部丟出來(不包含2)

  • any([A,B])
    it will return true if any value of this function is true

  • all([A,B])
    it will return true if all of the value is true

• complex

  • turn
    complex = 2+3j;
    num = complex(2,3)
    print(num2.real, num2.imag)

  2.0 3.0

• abs(絕對值) and round

  • print(abs(-5.5))

  5.5

• round

  • print(round(5.49, 1))

  5.5
  會收斂在小數點下面第一位

  • print(round(5.4))

  5

  • print(round(5.5))

  6

Enum

from enum import Enum

class State(Enum):
INACTIVE = 0
ACTIVE = 1

print(State.ACTIVE.value)
output: 1

print(State(1))
output: State.ACTIVE

print(State['ACTIVE'].value)
output: 1

print(list(State))
output <State.INACTIVE: 0>,<State.Active: 1>

print(let(State))
2

Basic input output

age = input("what is your age?\n")
print("your age is "+age)
output:
what is your age?
55
your age is 55

List

dogs = ["Roger",1,"Syd",True]

print("If Roger is in the list just print True\n")
print("Roger" in dogs)

print(dog[:3])
['Roger',1,'Sys']

print(len(dogs))
4

• append & edit

  • edit

  dogs[2]=beau
  print(dog[2])
  beau

  • append
    dogs.append('Judah')
    會把Judah加到最後面的分項去
  • extend
    dogs.extend(['Judah',5])
    把兩格分項都加到後面去，可以加一整個list
    • dogs+=['Judah',5]跟上面的結果是相同的

  若把Append加上list，整個list會變成最後分項，而不是多個獨立的。

  但若是寫成Dogs +="Judah"整個會被拆成'J','u','d','a','h'，所以一定要記得加上[]

  • remove(移除)
    dogs.remove('Syd')
    • 這樣syd會從裡面被移除，但要小心確認他有在list裡面，沒有整個program就會error。
  • pop
    remove the last item in the list , and print it.
    And this thing will not on the list anymore.
  • insert
    items.insert(2,"test")
    這樣item的第三項(從零開始算的)就會插入test，本來的index 2位置的，就會往後排。

  但你若是要插入多個的話，可以試試看這個

  items[1:1]=["test1","test2"]
  這樣就會從index 1開始插入test1跟test2，其他的項目往後遞延

  sort

  • items.sort()
    會把items這個list由大寫的第一個字順序到小寫的第一個字順序來排序。
  • items.sort(key=str.lower)
    會不分大小寫，照alphabet的順序來先做排列。
  • itemscopy=items[:]
    可以先行複製item內容，讓值被變更的同時可以保留他的原本樣貌
  • print(sorted(items,key=str.lower))
    可以不變動本來item的樣子，只有輸出時來做排列改變

  ---

Tuples

Tuple用()表示，Tuple一旦建立就不可再變更，要新增元素的話只能創新的Tuple後面再加。
you can't modify the original tuple

names = ("Roger", "Syd")
newTuple=names+("Tina","Quincy")

Dictionaries

• dog={"name":"Roger", "age":8, "color":"green"}
  print(dog.get("color","brown"))

  輸出狗的顏色，若是沒有就輸出brown

  • print(dog.pop("name"))
    print(dog)

  此時name就會消失，因為被pop掉了

  • print(dog.popitem())

  最後被加入的會被拿掉，是Color會消失

  • print(dog.keys())

  輸出所有的值
  dict_keys(['name','age,'color'])

  • print(list(dog.values()))

  ['Roger',8,'green']
  因為使用了List所以變成[]

  • dog["favorite food"]="meat"
    這樣最後就可以輸出多一項favorite food, meat
  • del dog['color']
    這樣就可以把顏色刪除
  • copy()
    dogCopy = dog.copy()
    這樣就可以copy dictionary

sets