100 Days of Code - The Complete Python Pro Bootcamp(Day2)

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Understanding Data Types and How To Manipulate Strings

Python Primitive Data Types

String

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'Hello'[0] #Can get a first character of a string
#This method of pulling out a particular element from a string is called sub-scripting.
print('Hello'[len('Hello')-1])
print('123' + '345') # 123345

Integer

Number data type one of the most common that you’ll see is called an integer.

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123 + 345 # 468
print(123_456_789) # we can replace big numbers commas simply with underscores 
# and it will be interpreted by the computer as if you had written this. 
# So the computer actually removes those underscores and ignores it.

Float

Decimal number they are called a float and this is short for a floating-point number.

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3.14159

# string to float bmi practice
weight = input('weight')
height = input('height')

bmi = float(weight) / float(height) / float(height)

print(bmi)

# 小數點後只有一位但要秀出兩位
"{:.2f}".format(12.5)

Boolean

Only two possible value true or false

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True
False

Type Error, Type Checking and Type Conversion

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num_char = len(input("What's your name?"));
print("your name has" + num_char + "characters."); # TypeError: can only concatenate str (not "int") to str

type(num_char) # use this to see type of this variable

# type conversion change data from a int to string
new_num_char = str(num_char)
print("your name has" + new_num_char + "characters.")

exercise 2.1

write a program that adds the digits in a 2 digit number. e.g. if the input was 35, then the output should be 3 + 5 = 8

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two_digit_number = input("Type a two digit number: ")
print(int(two_digit_number[0]) + int(two_digit_number[1]))

Mathematical Operations in Python

運算優先順序：PEMDAS(Parentheses, Exponents, Multiplication, Division, Addition, Subtration)
如相同等級如，乘除相同等級，由左到右依序計算。

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3 + 5

7 - 4

3 * 8

type(6 / 3) # float because the answer is 2.0 

2**2  # get a exponent number to a power

Number Manipulation and F Strings in Python

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round(8/3, 2) # 四捨五入，第二個參數可以設定到第幾位

#floor division 若只想取整數可用下方這樣寫
print(8//3) # 用type 檢查他會是一個int

score = score + 1 # 可寫成
scoer += 1 ## -= *= /= 同理

f-string 不用自己做型別轉換串起字串

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score = 0
height = 1.8
isWinning = True

f"Hello Clayton you score is {score}"