playground_05_io

Playground 05 - Input/Output

• String formatting
• Console IO
• File IO
• Error Handling

String formatting

Good reference

Top

# using concatenation. str is meant to give a user-friendly string representation of the object
print("1 + 1 = " + str(1 + 1))
# print("1 + 1 = " + repr(1+1)) #repr is the basically the same as str. It's meant to overriden on classes to give a interpreter-friendly string representation of the object
print("1 + 1 = {}".format(1 + 1))  # using the string's format method()
print("1 + 1 = %d" % (1 + 1))  # C-like

from math import pi
from math import e
print("pi = {1}\ne = {0}".format(e, pi))
print("pi = {1:.15f}\ne = {0:.15f}".format(e, pi))
print("pi = {pi:.15f}\ne = {nepper:.15f}".format(pi=pi, nepper=e))

Console IO

Python provides two built-in functions to read a line of text from standard input, which by default comes from the keyboard. Good reference

Top

# input() is used for everything
number = input()
print(number)

string = str(input())
print(string)

myList = input().split(" ")
print(myList)

#print is used for every other console output operation

File IO

Good reference

Top

# available modes: r, w, r+, a, rb, wb, rb+, ab
# "utf-8" is useful for portugues chars
textFile = open("exampleFile.txt", "r", encoding="utf-8") 
print(textFile.read())  # reads everythig
textFile.seek(0)  # goes back to the file start
print(textFile.read(15))  # "Hello, how are
textFile.seek(0)
print(textFile.readline())  # "Hello, how are you?"

textFile.seek(0)
for line in textFile:
    # optional argument end determines what the character at the end of a print will be. By default it is \n
    print(line, end="")

# should be closed afterwards to avoid wasting resources
textFile.close()

textFile = open("newTextFile.txt", "r+")
aTranscript = """\
As Ethel descended the wooden staircase with her two puppies in pursuit, her grandmother called from the living room.

"Ethel, dear! Dinner is ready!"

"I'm coming grandma!" she replied
"""
textFile.write(aTranscript)

textFile.seek(0)

print(textFile.read())

textFile.close()

Error Handling

Python provides two very important features to handle any unexpected error in your Python programs and to add debugging capabilities in them.

Good reference

Top

try:
    10 / 0
except ZeroDivisionError:
    print("Please don't divide by zero. Computers don't enjoy that.")
finally:
    print("Whatever you did, we're out of here")


option = 0
while True:
    try:
        option = int(input("Choose an option"))
        break
    except ValueError:
        print("Please type in a number!")
    finally:
        print("You'll see me at the end of every loop")

Top