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Transcript of Python: Part 3 - National Institute for · PDF filePython: Part 3 Daniel Lucio Python Crash...

  • Python: Part 3Daniel Lucio

    Python Crash CourseApril 6, 2016

  • Python Crash Course

    Sublime Text 3

    https://www.sublimetext.com/

  • Python Crash Course

    Setting Up Sublime Text 3 for Python3 Development

    Go to tools -- build system -- new build system

    { "cmd": ["/usr/local/bin/python3", "-u", "$file"], "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)", "selector": "source.python", "encoding": "utf8", "path": "/usr/local/Frameworks/Python.framework/Versions/3.5/bin/"}

    http://www.jasred.com/2014/05/12/setting-up-sublime-text-3-for-python3-development/

  • Python Crash Course

    Celcius to Fahrenheit

    In this formula, C is the amount of degrees in Celsius, and F is the corresponding temperature measured in Fahrenheit. Our goal now is to write a computer program which can

    compute F from when C is known.

    F =9

    5C + 32

  • Python Crash Course

    61 Chapter 4: Reviewing Basic Python

    Doing arithmeticStoring information in variables makes it easily accessible. However, in order to perform any useful work with the variable, you usually perform some type of arithmetic operation on it. Python supports the common arithmetic opera-tors you use to perform tasks by hand. They appear in Table 4-2.

    Sometimes you need to interact with just one variable. Python supports a number of unary operators, those that work with just one variable, as shown in Table 4-3.

    Table 4-2 Python Arithmetic OperatorsOperator Description Example+ Adds two values together 5 + 2 = 7 Subtracts the righthand operand from left operand 5 2 = 3* Multiplies the righthand operand by the left operand 5 * 2 = 10/ Divides the lefthand operand by the right operand 5 / 2 = 2.5% Divides the lefthand operand by the right operand and

    returns the remainder5 % 2 = 1

    ** Calculates the exponential value of the right operand by the left operand

    5 ** 2 = 25

    // Performs integer division, in which the left operand is divided by the right operand and only the whole number is returned (also called floor division)

    5 // 2 = 2

    Table 4-3 Python Unary OperatorsOperator Description Example~ Inverts the bits in a number so that all of the 0 bits

    become 1 bits and vice versa.~4 results in a value of 5

    Negates the original value so that positive becomes negative and vice versa.

    (4) results in 4 and 4 results in 4

    + Is provided purely for the sake of completeness. This operator returns the same value that you provide as input.

    +4 results in a value of 4

  • Python Crash Course

    64 Part I: Getting Started with Python for Data Science

    Computers provide order to comparisons by making some operators more significant than others. The ordering of operators is operator precedence. Table 4-7 shows the operator precedence of all the common Python opera-tors, including a few you havent seen as part of a discussion yet. When making comparisons, always consider operator precedence because other-wise, the assumptions you make about a comparison outcome will likely be wrong.

    Operator Description Exampleor Determines when one of two

    operands is true.True or True is True

    True or False is True

    False or True is True

    False or False is Falsenot Negates the truth value of a

    single operand. A true value becomes false and a false value becomes true.

    not True is False

    not False is True

    Table 4-6 (continued)

    Table 4-7 Python Operator PrecedenceOperator Description() You use parentheses to group expressions and to override

    the default precedence so that you can force an operation of lower precedence (such as addition) to take precedence over an operation of higher precedence (such as multiplication).

    ** Exponentiation raises the value of the left operand to the power of the right operand.

    ~ + Unary operators interact with a single variable or expression.* / % // Multiply, divide, modulo, and floor division.+ Addition and subtraction.>> = Comparison operators.

  • Python Crash Course

    C2F, v1What is the equivalent of 21C?

    print((9/5)*21+32)

  • Python Crash Course

    C2F, v2 (Using Variables)What is the equivalent of 21C?

    c=21f=(9/5)*c+32print(f)

  • Python Crash Course

    C2F, v3 (Using Functions)What is the equivalent of 21C?

    defc2f(c):return((9/5)*c+32)

    print(c2f(21))

  • Python Crash Course

    C2F, v4 (Using Functions)What is the equivalent of 21C?

    defc2f(c):return((9/5)*c+32)

    print(c2f(21))

  • Python Crash Course

    C2F (Looping)How to create a conversion table?

    -20-4.0-155.0-1014.0-523.0032.0541.01050.01559.02068.02577.03086.03595.040104.0

    C F

  • Python Crash Course

    63 Chapter 4: Reviewing Basic PythonSometimes a relational operator cant tell the whole story of the comparison of two values. For example, you might need to check a condition in which two

    separate comparisons are needed, such as MyAge > 40 and MyHeight < 74. The need to add conditions to the comparison requires a logical operator of the sort shown in Table 4-6.

    Table 4-5 Python Relational OperatorsOperator Description Example== Determines whether two values are equal. Notice

    that the relational operator uses two equals signs. A mistake many developers make is using just one equals sign, which results in one value being assigned to another.

    1 == 2 is False

    != Determines whether two values are not equal. Some older versions of Python allowed you to use the operator in place of the != operator. Using the operator results in an error in current versions of Python.

    1 != 2 is True

    > Verifies that the left operand value is greater than the right operand value.

    1 > 2 is False

    < Verifies that the left operand value is less than the right operand value.

    1 < 2 is True

    >= Verifies that the left operand value is greater than or equal to the right operand value.

    1 >= 2 is False

  • Python Crash Course

    C2F, v5 (while loop)How to create a conversion table for -20 to 40C?

    c=-20whilec

  • Python Crash Course

    60 Part I: Getting Started with Python for Data Science

    Performing variable assignmentsWhen working with applications, you store information in variables. A vari-able is a kind of storage box. Whenever you want to work with the informa-tion, you access it using the variable. If you have new information you want to store, you put it in a variable. Changing information means accessing the variable first and then storing the new value in the variable. Just as you store things in boxes in the real world, so you store things in variables (a kind of storage box) when working with applications. To store data in a variable, you assign the data to it using any of a number of assignment operators (special symbols that tell how to store the data). Table 4-1 shows the assignment operators that Python supports.

    Table 4-1 Python Assignment OperatorsOperator Description Example= Assigns the value found in the right operand

    to the left operandMyVar = 2 results in MyVar containing 2

    += Adds the value found in the right operand to the value found in the left operand and places the result in the left operand

    MyVar += 2 results in MyVar containing 7

    = Subtracts the value found in the right oper-and from the value found in the left operand and places the result in the left operand

    MyVar = 2 results in MyVar containing 3

    *= Multiplies the value found in the right oper-and by the value found in the left operand and places the result in the left operand

    MyVar *= 2 results in MyVar containing 10

    /= Divides the value found in the left operand by the value found in the right operand and places the result in the left operand

    MyVar /= 2 results in MyVar containing 2.5

    %= Divides the value found in the left operand by the value found in the right operand and places the remainder in the left operand

    MyVar %= 2 results in MyVar containing 1

    **= Determines the exponential value found in the left operand when raised to the power of the value found in the right operand and places the result in the left operand

    MyVar ** 2 results in MyVar containing 25

    //= Divides the value found in the left operand by the value found in the right operand and places the integer (whole number) result in the left operand

    MyVar //= 2 results in MyVar containing 2

  • Python Crash Course

    C2F, v6 (while loop)How to create a conversion table for -20 to 40C?

    c=-20whilec

  • Python Crash Course

    C2F, v7 (for loop)How to create a conversion table for -20 to 40C?

    degrees=[-20,-15,-10,-5,0,5,10,15,20,25,30,35,40]forcindegrees: print(c,(9/5)*c+32)

    forcinrange(-20,45,5): print(c,(9/5)*c+32)

  • Python Crash Course

    C2F, v9 (pretty print)How to create a conversion table for -20 to 40C?

    forcinrange(-20,45,5): print(c,(9/5)*c+32)

    forcinrange(-20,45,5):print('%5d%5.1f'%(c,(9/5)*c+32))

    vs

    forcinrange(-20,45,5): print('{0:5d}{1:5.1f}'.format(c,(9/5)*c+32))

    vs

  • Python Crash Course

    C2F, v10 (Nested Lists)How to create a conversion table for -20 to 40C?

    Cdegrees=range(-20,45,5)Fdegrees=[(9.0/5)*C+32forCinCdegrees]table=[]forC,Finzip(Cdegrees,Fdegrees):table.append([C,F])print(table)

  • Python Crash Course

    C2F, v11 (Nested Lists)How to create a conversion table for -20 to 40C?

    importpprintCdegrees=range(-20,45,5)Fdegrees=[(9.0/5)*C+32forCinCdegrees]table=[]forC,Finzip(Cdegrees,Fdegrees):table.append([C,F])pprint.pprint(table)

  • Python Crash Course