'''
# Some tools for the labs
# min, max, round
print(max(15.7,2,16.2,8))
print(min(16.2,6))
print("---")
print(round(14.9999999999))
print(round(15.5))
print(round(15.4999999999))
# Files
- FILES are a valuable tool to help us solve many
types of problems.
FILES give us PERSISTENCE
- So far, we've been running our programs in IDLE and
putting our code into a file.
* Data must be entered on every program run
* Programs have no way to write permanent output
- With PERSISTENCE, our data can be "saved" between
each program execution.
FILE BASICS:
- We can store files in many different forms
- Examples: .xls, .docx, .pdf, .jpg, ...
- For this class, we'll just deal with "plain text"
files (.txt)
- These CHARACTERS are represented in something called
ASCII (American Standard Code for Information Interchange)
- This was dominant / simple way of representing text
where each character is 8 bits long
- UTF-8 is the most popular format in today's web browsers
- Allows us to represent MANY characters from multiple
languages
TERMS:
File: A document
Directory: A folder containing files and other folders
File System: Collection of all the files and folders on the
computer, organized in a heirarchy
For this class, we'll deal with reading and writing files
that are in the same directory as our .py file (known as
our "working directory"
- This makes our lives much easier
The Unix File system:
- In unix the directory at the highest level of the hierarchy is called the root (denoted by /). All other directories and files are stored within the root
- Path: The path is a sequence (of directories) that specifies the location of a file or directory within the file system. For example, /Users/diba/ says that the directory diba is within the directory Users which is within the root
* An ABSOLUTE path describes the location of a file or directory starting with the root (/)
* A RELATIVE path describes the location of a file relative to the current directory. For example ./cs8/lab05/ (Here './' stands for "current directory" )
- You can move through the unix file system via the command line (instead of using the graphical interface)
- Few useful unix commands
- pwd (path to your current working directory)
- ls (list all the files and directories within the current directory)
- mkdir (make a new directory)
- cd (change into a directory, need to give either absolute or relative path)
FILE I/O:
- I/O stands for input / output
- We read data from a file into our program.
- We write data from our program into a file.
- Steps for File I/O
1. Open the file (creates a "connection" between your
program and the file).
- Choose if the connection will be for reading,
writing, or appending to a file.
2. Read the data / write the data
3. Close the file (close the "connection"). This should
to be done once per file.
Common ways to read data from files
1. read() method - reads the entire file into one string
- Good for small data (large files may be too big to
store into memory)
2. read(n): Read the next n characters from the input
- Better for larger files since you only need to store
n characters in memory at a time.
3. readline(): Reads everything from the current position
to the next '\n' (or to the end of the file, 'EOF'). If
nothing left to read, .readline() returns an empty string.
4. readlines(): Reads all the lines in the file and returns
a list.
5. for a_line in infile:
- a_line represents a line in the file, infile is the
open file.
'''
'''
# Example reading from 'example.txt'
infile = open('example.txt', 'r')
data = infile.read()
print(data)
infile.close()
'''
'''
# Example writing to a file 'example_2.txt'
outfile = open('example_2.txt', 'w')
outfile.write("Duck\nCow\nCat")
outfile.close()
'''
'''
# Create a list of lines in the file
infile = open('example.txt', 'r')
datalines = infile.readlines() # returns a list of strings
print(datalines)
infile.close()
'''
'''
# Write "overwrites" the existing file
outfile = open("example.txt", 'w')
outfile.write("Something new!\n")
outfile.write("Another line!")
outfile.close()
'''
'''
# Append to an existing file
outfile = open("example.txt", 'a')
outfile.write("Something else!\n")
outfile.write("Yet another line.")
outfile.close()
'''
'''
# read(n)
infile = open("example.txt", 'r')
data = infile.read(3)
print(data)
data = infile.read(6)
print(data)
infile.close()
'''
'''
# readline example
infile = open("example.txt", 'r')
line = infile.readline()
print(line)
line = infile.readline()
print(line)
infile.close()
'''
'''
# Example of copying / writing to another file
infile = open('example.txt', 'r')
outfile = open('copy.txt', 'w')
for line in infile:
outfile.write(line)
infile.close()
outfile.close()
# STRING FUNCTIONS
# We've seen several of these - .split(), .strip()
# We'll introduce some more...
s = "CS 8: Intro to Programming"
'''
print("Where does the first 'mm' occur in s?")
print(s.find("mm"))
print(s.find("jfklahgl"))
text = """This
string
has
multiple
lines"""
first_newline = text.find("\n")
print("First newline position:", text.find("\n"))
print("First line of text:", text[:first_newline])
print("String after first newline:", text[first_newline + 1:])
'''
'''
# .startswith method
print("Check if s starts with 'CS':", s.startswith("CS"))
print("Check if s starts with 'Computer':", s.startswith("Computer"))
# .endswith method
print("Check if s ends with 'P':", s.endswith("P"))
print("Check if s ends with 'inG':", s.endswith("inG"))
print("Check if s ends with 'ing':", s.endswith("ing"))
# .count method
print("Times 'm' is in s:", s.count("m"))
print("Times 'i' is in 'Mississippi':", 'Mississippi'.count('i'))
MS = "Mississippi"
print("Times 'ss' is in 'Mississippi':", MS.count('ss'))
# .replace method
print("Change all 'i' to '!' in 'Mississippi':", MS.replace("i", "!"))
print("Change all ':' to '#' in s:", s.replace(":", "#"))
print("Remove all 'i' in 'Mississippi':", MS.replace("i",""))
# Strings are immutable (these methods won't change the string)
print(s)
print(MS)
# Change the value with reassignment
s = s.replace("m", "M")
print(s)
# upper / lower case
print(s.lower())
print(s.upper())
print(s) # still didn't change
'''
# Examples of String formatting
price = 18.00
print("The price is ${}. That's cheap!".format(price))
print("The price is ${}. {}.".format(price,"wow!"))
print("{3:} {2:} {1:} {0:}".format('a','b','c','d'))
''' Format specification:
{ : }. Left side of colon say which argument to place into {}
To the right we specify a FIELD WIDTH (i.e., how many spaces/
columns on the screen to devote to this
'''
'''
print("-->{}<--".format(price))
print("-->{:20}<--".format(price))
print("-->{:20}<--".format("18"))
# We can use '>' or '<' to justify left or right
print("-->{:<20}<--".format("18"))
print("-->{:>20}<--".format("18"))
# we can use '^' to center.
print("-->{:^20}<--".format("18"))
'''
print("-->{:20.2f}<--".format(price))
# without 'f' , price appears in scientific notation
# More examples
price = 12345.6
print("-->{:10.2f}<--".format(price))
print("-->{:6.2f}<--".format(price))
# can identify specific types that should be expected with
# 's'- string, 'd' - int, 'f' - float
name = "Chris Gaucho"
age = 21
print("Name is {:12s}; age is {:2d}; price is ${:0.2f}".format(name,age,price))
print("Name is {:12}; age is {:2}; price is ${:0.2}".format(name,age,price))
# still works if s,d,f is not included, but removing 'f' will look strange
'''