7.10: Python Examples

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Page ID: 10697

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Strings

# This program demonstrates string functions.


def main():
    string = "Hello"

    print("string: " + string)
    print("string.lower(): " + string.lower())
    print("string.upper(): " + string.upper())
    print("string.find('e'): " + str(string.find('e')))
    print("len(string): " + str(len(string)))
    print("string.replace('H', 'j'): " + string.replace('H', 'j')) 
    print("string[::-1]: " + string[::-1])
    print("string[2:4]: " + string[2:4])
    print("string.strip('H'): " + string.strip('H'))

    name = "Bob"
    value = 123.456
    print("string.format(): {0} earned ${1:.2f}".format(name, value))


main()

Output

string: Hello
string.lower(): hello
string.upper(): HELLO
string.find('e'): 1
len(string): 5
string.replace('H', 'j'): jello
string[::-1]: olleH
string[2:4]: ll
string.strip('H'): ello
string.format(): Bob earned $123.46

Files

# This program creates a file, adds data to the file, displays the file,
# appends more data to the file, displays the file, and then deletes the file.
# It will not run if the file already exists.
#
# References:
#     https://www.mathsisfun.com/temperature-conversion.html
#     https://en.wikibooks.org/wiki/Python_Programming


import os
import sys


def calculate_fahrenheit(celsius):
    fahrenheit = celsius * 9 / 5 + 32    
    return fahrenheit


def create_file(filename):
    try:
        file = open(filename, "w")
        file.write("Celsius,Fahrenheit\n")
        for celsius in range(0, 51):
            fahrenheit = calculate_fahrenheit(celsius)
            file.write("{:.1f},{:.1f}\n".format(celsius, fahrenheit))
        file.close()
    except:
        print("Error creating", filename)
        print(sys.exc_info()[1])


def read_file(filename):
    try:
        file = open(filename, "r")
        for line in file:
            line = line.strip()
            print(line)
        file.close()
        print()
    except:
        print("Error reading", filename)
        print(sys.exc_info()[1])


def append_file(filename):
    try:
        file = open(filename, "a")
        for celsius in range(51, 101):
            fahrenheit = calculate_fahrenheit(celsius)
            file.write("{:.1f},{:.1f}\n".format(celsius, fahrenheit))
        file.close()
    except:
        print("Error appending to", filename)
        print(sys.exc_info()[1])


def delete_file(filename):
    try:
        os.remove(filename)
    except:
        print("Error deleting", filename)
        print(sys.exc_info()[1])


def main():
    filename = "~file.txt"

    if os.path.isfile(filename):
        print("File already exists.")
    else:
        create_file(filename)
        read_file(filename)
        append_file(filename)
        read_file(filename)
        delete_file(filename)
        

main()

Output

Celsius,Fahrenheit
0.0,32.0
1.0,33.8
2.0,35.6
3.0,37.4
...
98.0,208.4
99.0,210.2
100.0,212.0

References

Wikiversity: Computer Programming