Reading the data

This section uses the same data file that we just saw. If you want to see all of the data click on the Show button below. Once it appears, you can hide it again by clicking on the Hide button.

Aberdeen, SD :13 :8
Adrian, MI :15 :9
Akron, OH :18 :11
Albany, GA :18 :11
Albany-Lebanon, OR :14 :8
Albany-Schenectady-Troy, NY :13 :8
Albuquerque, NM :12 :7
Alexandria, LA :20 :12
Allegan, MI :14 :9
Allentown-Bethlehem-Easton, PA-NJ :21 :12
Altoona, PA :19 :12
Anchorage, AK :13 :8
Anderson, IN :18 :11
Ann Arbor, MI :16 :10
Appleton, WI :14 :9
Asheville, NC :15 :9
Athens, OH :14 :9
Athens, TN :15 :9
Athens-Clarke County, GA :16 :9
Atlanta-Sandy Springs-Marietta, GA :23 :14
Atlantic City-Hammonton, NJ :14 :8
Augusta-Richmond County, GA-SC :18 :11
Augusta-Waterville, ME :14 :9
Austin-Round Rock, TX :17 :10
Bakersfield, CA :24 :15
Baltimore-Towson, MD :20 :12
Bangor, ME :12 :7
Baraboo, WI :17 :10
Baton Rouge, LA :19 :11
Bay City, MI :13 :8
Beaver Dam, WI :15 :9
Beckley, WV :14 :8
Bellingham, WA :7 :4
Bennington, VT :11 :7
Birmingham-Hoover, AL :20 :12
Bishop, CA :11 :6
Bismarck, ND :11 :6
Bloomington, IN :17 :10
Bloomington-Normal, IL :16 :9
Boise City-Nampa, ID :17 :10
Boone, NC :13 :8
Boston-Cambridge-Quincy, MA-NH :16 :10
Boulder, CO :12 :7
Bowling Green, KY :17 :10
Bradenton-Sarasota-Venice, FL :12 :7
Brainerd, MN :8 :5
Bremerton-Silverdale, WA :7 :4
Bridgeport-Stamford-Norwalk, CT :16 :9
Brigham City, UT :12 :7
Brookings, SD :14 :9
Brownsville-Harlingen, TX :16 :10
Brunswick, GA :13 :8
Buffalo-Niagara Falls, NY :16 :9
Burlington, NC :14 :9
Burlington-South Burlington, VT :12 :7
Butte-Silver Bow, MT :19 :11
Cadillac, MI :10 :6
Cambridge, MD :13 :8
Canton-Massillon, OH :21 :12
Cape Coral-Fort Myers, FL :12 :7
Casper, WY :9 :5
Cedar Rapids, IA :16 :10
Champaign-Urbana, IL :16 :10
Charleston, WV :18 :11
Charleston-North Charleston-Summerville, SC :16 :10
Charlotte-Gastonia-Concord, NC-SC :16 :10
Charlottesville, VA :13 :8
Chattanooga, TN-GA :18 :11
Cheyenne, WY :9 :6
Chicago-Naperville-Joliet, IL-IN-WI :22 :13
Chico, CA :12 :7
Cincinnati-Middletown, OH-KY-IN :23 :14
Clarksburg, WV :16 :10
Clarksville, TN-KY :16 :10
Clearlake, CA :7 :4
Cleveland-Elyria-Mentor, OH :24 :15
Clinton, IA :18 :11
Colorado Springs, CO :12 :7
Columbia, SC :17 :10
Columbia, TN :14 :8
Columbus, GA-AL :19 :11
Columbus, OH :18 :11
Concord, NH :16 :9
Cookeville, TN :14 :9
Corning, NY :11 :7
Corpus Christi, TX :18 :11
Dallas-Fort Worth-Arlington, TX :20 :12
Daphne-Fairhope-Foley, AL :15 :9
Davenport-Moline-Rock Island, IA-IL :18 :11
Dayton, OH :18 :11
Decatur, AL :15 :9
Decatur, IL :17 :10
Deltona-Daytona Beach-Ormond Beach, FL :11 :6
Denver-Aurora-Broomfield, CO :14 :9
Des Moines-West Des Moines, IA :15 :9
Detroit-Warren-Livonia, MI :21 :12
Dickinson, ND :7 :4
Dothan, AL :15 :9
Dover, DE :14 :8
Duluth, MN-WI :11 :6
Durango, CO :7 :4
Durham, NC :14 :8
Durham-Chapel Hill, NC :14 :8
Dyersburg, TN :15 :9
East Stroudsburg, PA :13 :8
Eau Claire, WI :14 :8
El Centro, CA :24 :14
El Dorado, AR :18 :11
El Paso, TX :21 :12
Elizabethtown, KY :20 :12
Elkhart-Goshen, IN :21 :12
Erie, PA :19 :11
Eugene-Springfield, OR :13 :8
Eureka-Arcata-Fortuna, CA :11 :7
Evansville, IN-KY :19 :12
Fairbanks, AK :31 :19
Fairmont, WV :17 :10
Fargo, ND-MN :13 :8
Farmington, NM :8 :5
Fayetteville, NC :15 :9
Fayetteville-Springdale-Rogers, AR-MO :16 :10
Flagstaff, AZ :9 :5
Flint, MI :13 :8
Florence, SC :15 :9
Florence-Muscle Shoals, AL :15 :9
Fort Collins-Loveland, CO :12 :7
Fort Madison-Keokuk, IA-MO :18 :11
Fort Payne, AL :15 :9
Fort Smith, AR-OK :17 :10
Fort Wayne, IN :23 :14
Fresno, CA :74 :45
Gadsden, AL :16 :10
Gainesville, FL :12 :7
Gainesville, GA :16 :9
Gettysburg, PA :18 :11
Gillette, WY :13 :8
Goldsboro, NC :21 :13
Grand Island, NE :13 :8
Grand Junction, CO :12 :7
Grand Rapids-Wyoming, MI :16 :10
Grants Pass, OR :12 :7
Greeley, CO :13 :8
Green Bay, WI :16 :10
Greensboro-High Point, NC :14 :9
Greenville, NC :13 :8
Greenville-Mauldin-Easley, SC :16 :10
Grenada, MS :16 :9
Gulfport-Biloxi, MS :16 :10
Hagerstown-Martinsburg, MD-WV :19 :11
Hammond, LA :15 :9
Hanford-Corcoran, CA :28 :17
Harriman, TN :22 :13
Harrisburg-Carlisle, PA :20 :12
Harrisonburg, VA :15 :9
Hartford-West Hartford-East Hartford, CT :14 :9
Hattiesburg, MS :18 :11
Helena, MT :16 :9
Helena-West Helena, AR :16 :9
Hickory-Lenoir-Morganton, NC :16 :10
Hilo, HI :27 :16
Hobbs, NM :13 :8
Holland-Grand Haven, MI :15 :9
Homosassa Springs, FL :11 :7
Honolulu, HI :12 :7
Hot Springs, AR :18 :11
Houma-Bayou Cane-Thibodaux, LA :13 :8
Houston-Sugar Land-Baytown, TX :21 :13
Huntington-Ashland, WV-KY-OH :19 :11
Huntsville, AL :16 :9
Indianapolis-Carmel, IN :25 :15
Iowa City, IA :16 :10
Jackson, MS :19 :11
Jackson, TN :15 :9
Jackson, WY-ID :11 :6
Jacksonville, FL :13 :8
Jamestown-Dunkirk-Fredonia, NY :13 :8
Jasper, IN :18 :11
Johnstown, PA :19 :12
Juneau, AK :11 :6
Kahului-Wailuku, HI :11 :6
Kalamazoo-Portage, MI :17 :10
Kalispell, MT :13 :8
Kansas City, MO-KS :24 :15
Kapaa, HI :11 :7
Keene, NH :16 :10
Kingsport-Bristol-Bristol, TN-VA :15 :9
Kinston, NC :13 :8
Klamath Falls, OR :18 :11
Knoxville, TN :18 :11
Kokomo, IN :16 :10
La Crosse, WI-MN :14 :8
Laconia, NH :11 :7
Lafayette, IN :24 :14
Lafayette, LA :18 :11
Lake Charles, LA :14 :8
Lake Havasu City-Kingman, AZ :6 :4
Lakeland-Winter Haven, FL :13 :8
Lancaster, PA :21 :13
Lansing-East Lansing, MI :14 :9
Laramie, WY :9 :6
Las Cruces, NM :25 :15
Las Vegas-Paradise, NV :20 :12
Laurel, MS :18 :11
Lawrenceburg, TN :14 :8
Lebanon, NH-VT :11 :7
Lebanon, PA :24 :14
Lewiston-Auburn, ME :13 :8
Lexington-Fayette, KY :16 :10
Lima, OH :17 :10
Lincoln, NE :14 :9
Little Rock-North Little Rock-Conway, AR :19 :12
Logan, UT-ID :15 :9
Los Angeles-Long Beach-Santa Ana, CA :33 :20
Louisville/Jefferson County, KY-IN :22 :13
Lumberton, NC :14 :9
Lynchburg, VA :13 :8
Macon, GA :19 :12
Madera, CA :27 :16
Madison, WI :16 :9
Manchester-Nashua, NH :14 :8
Marshall, MN :12 :7
Marshall, TX :17 :10
McAlester, OK :19 :11
McAllen-Edinburg-Mission, TX :18 :11
Medford, OR :15 :9
Memphis, TN-MS-AR :17 :10
Merced, CA :18 :11
Meridian, MS :17 :10
Miami-Fort Lauderdale-Pompano Beach, FL :14 :8
Michigan City-La Porte, IN :16 :10
Middlesborough, KY :17 :10
Milwaukee-Waukesha-West Allis, WI :18 :11
Minneapolis-St. Paul-Bloomington, MN-WI :17 :10
Missoula, MT :21 :12
Mobile, AL :15 :9
Modesto, CA :25 :15
Monroe, LA :22 :13
Monroe, MI :16 :9
Montgomery, AL :18 :11
Morgantown, WV :15 :9
Mount Vernon, IL :14 :9
Muncie, IN :16 :10
Muscatine, IA :18 :11
Muskegon-Norton Shores, MI :15 :9
Napa, CA :23 :14
Nashville-Davidson--Murfreesboro--Franklin, TN :17 :10
New Castle, IN :15 :9
New Haven-Milford, CT :15 :9
New Orleans-Metairie-Kenner, LA :21 :13
New York-Northern New Jersey-Long Island, NY-NJ-PA :23 :14
Niles-Benton Harbor, MI :14 :9
Nogales, AZ :16 :10
Norwich-New London, CT :13 :8
Ogden-Clearfield, UT :15 :9
Oklahoma City, OK :16 :10
Omaha-Council Bluffs, NE-IA :19 :12
Orlando-Kissimmee, FL :12 :7
Owensboro, KY :18 :11
Oxnard-Thousand Oaks-Ventura, CA :16 :10
Paducah, KY-IL :17 :10
Palm Bay-Melbourne-Titusville, FL :10 :6
Parkersburg-Marietta-Vienna, WV-OH :17 :10
Pascagoula, MS :15 :9
Pendleton-Hermiston, OR :12 :7
Pensacola-Ferry Pass-Brent, FL :14 :8
Peoria, IL :16 :10
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD :28 :17
Phoenix-Mesa-Scottsdale, AZ :26 :16
Pittsburgh, PA :25 :15
Pittsfield, MA :14 :9
Platteville, WI :15 :9
Pocatello, ID :15 :9
Ponca City, OK :17 :10
Portland-South Portland-Biddeford, ME :15 :9
Portland-Vancouver-Beaverton, OR-WA :12 :7
Portsmouth, OH :16 :10
Poughkeepsie-Newburgh-Middletown, NY :13 :8
Prescott, AZ :7 :4
Prineville, OR :14 :9
Providence-New Bedford-Fall River, RI-MA :18 :11
Provo-Orem, UT :14 :8
Pueblo, CO :11 :7
Quincy, IL-MO :16 :10
Raleigh-Cary, NC :16 :9
Rapid City, SD :11 :6
Reading, PA :19 :11
Red Bluff, CA :14 :8
Redding, CA :10 :6
Reno-Sparks, NV :15 :9
Richmond, VA :15 :9
Richmond-Berea, KY :15 :9
Riverside-San Bernardino-Ontario, CA :34 :21
Riverton, WY :13 :8
Roanoke, VA :15 :9
Rochester, MN :13 :8
Rochester, NY :14 :9
Rock Springs, WY :13 :8
Rockford, IL :16 :9
Rocky Mount, NC :13 :8
Rome, GA :18 :11
Russellville, AR :14 :9
Rutland, VT :15 :9
Sacramento--Arden-Arcade--Roseville, CA :15 :9
Salinas, CA :10 :6
Salisbury, NC :16 :9
Salt Lake City, UT :15 :9
San Antonio, TX :14 :9
San Diego-Carlsbad-San Marcos, CA :24 :14
San Francisco-Oakland-Fremont, CA :16 :10
San Jose-Sunnyvale-Santa Clara, CA :16 :10
San Luis Obispo-Paso Robles, CA :16 :10
Santa Barbara-Santa Maria-Goleta, CA :14 :9
Santa Cruz-Watsonville, CA :10 :6
Santa Fe, NM :8 :5
Santa Rosa-Petaluma, CA :14 :8
Sault Ste. Marie, MI :14 :8
Savannah, GA :17 :10
Scottsbluff, NE :9 :6
Scranton--Wilkes-Barre, PA :14 :8
Seaford, DE :14 :8
Seattle-Tacoma-Bellevue, WA :16 :10
Sheridan, WY :14 :8
Shreveport-Bossier City, LA :26 :16
Sierra Vista-Douglas, AZ :11 :7
Sioux City, IA-NE-SD :16 :10
Sioux Falls, SD :14 :9
Somerset, KY :16 :10
South Bend-Mishawaka, IN-MI :21 :13
Spartanburg, SC :16 :10
Spokane, WA :12 :7
Springfield, IL :16 :10
Springfield, MA :15 :9
Springfield, MO :17 :10
Springfield, OH :17 :10
St. Cloud, MN :14 :8
St. George, UT :11 :7
St. Joseph, MO-KS :20 :12
St. Louis, MO-IL :22 :13
State College, PA :19 :11
Stockton, CA :21 :12
Syracuse, NY :12 :7
Talladega-Sylacauga, AL :17 :10
Tallahassee, FL :14 :9
Tampa-St. Petersburg-Clearwater, FL :13 :8
Terre Haute, IN :19 :12
Texarkana, TX-Texarkana, AR :18 :11
Thomasville-Lexington, NC :17 :10
Toledo, OH :17 :10
Topeka, KS :14 :9
Torrington, CT :9 :6
Trenton-Ewing, NJ :15 :9
Truckee-Grass Valley, CA :10 :6
Tucson, AZ :10 :6
Tulsa, OK :16 :10
Tupelo, MS :16 :10
Tuscaloosa, AL :16 :9
Ukiah, CA :12 :7
Valdosta, GA :14 :9
Vallejo-Fairfield, CA :15 :9
Vernal, UT :12 :7
Virginia Beach-Norfolk-Newport News, VA-NC :14 :8
Visalia-Porterville, CA :25 :15
Warner Robins, GA :16 :10
Washington-Arlington-Alexandria, DC-VA-MD-WV :19 :12
Waterloo-Cedar Falls, IA :16 :10
Watertown, SD :18 :11
Weirton-Steubenville, WV-OH :20 :12
Wenatchee, WA :17 :10
Wheeling, WV-OH :20 :12
Wichita, KS :16 :9
Wilmington, NC :14 :9
Winchester, VA-WV :16 :10
Winston-Salem, NC :15 :9
Worcester, MA :15 :9
Yakima, WA :17 :10
York-Hanover, PA :20 :12
Youngstown-Warren-Boardman, OH-PA :23 :14
Yuba City, CA :12 :7
Yuma, AZ :14 :9

If you clicked on the Show button you can tell that it is a lot of data. But we don’t actually know the number of lines of data in the file by looking at it. Since we don’t know the number of lines here, we won’t use a for loop to process it. We will use a while loop to keep reading the data until there isn’t any more (returns an empty string).

We can process it by opening the file containing the data, then reading each line in. As long as the line is not empty, we keep going doing a split and processing the data. (This data is separated by a : instead of a ,.)

In Python, we must open files before we can use them and close them when we are done with them. Opening a file returns a Python object that has predefined functions and procedures, just like the turtle objects we have seen before. Table 1 shows the functions and procedures that can be used to open and close files.

Method Name Use Explanation
open open(filename,'r') Open a file called filename and use it for reading. This will return a reference to a file object.
open open(filename,'w') Open a file called filename and use it for writing. This will also return a reference to a file object.
close filename.close() Closes the file after you are finished with it.

The code below will print out the pollution information for all the cities that start with "A". It will print the city, state on one line and the two pollution values for that city on another line. It stops looping when there aren’t any more lines to be read (when the returned line is an empty string).

        csp-18-3-1: The following program prints the pollution information for all cities that start with a ``D``, but the code is mixed up.  Drag the blocks of statements from the left column to the right column and put them in the right order.  Then click on Check Me to see if you are right. You will be told if any of the lines are in the wrong order or have the wrong indention.# open the file for reading
inFile = open("uspoll.txt","r")

# read a line from the file
line = inFile.readline()
---
# while there is another line
while line:
---
    # split at the :
    v = line.split(":")

    # get the city
    city = v[0]
---
    # if city starts with an D print info
    if (city.find("D") == 0):
        print('City: ', city)
        print("Pollution values:",v[1],v[2])
---
    # read the next line
    line = inFile.readline()
---
# close the file
inFile.close()
        

There is actually a way of using a for loop to read in a file. We can read the whole thing into one giant list, and then use a for loop to process each line in the list.

    csp-18-3-2: What is the disadvantage of the second program, with a for loop?
  • For a big data file, this could overload memory.
  • This will be true for very large data sets.
  • for loops are inefficient.
  • for loops and while loops have the same efficiency.
  • for loops are not as flexible as while loops.
  • while loops are flexible, but for loops are more understandable, so you should use what makes the most sense for you.

Write code to that will read an input file uspoll.txt . It will print the city name and the pollution values for all cities that have a PM 10 pollution of 20 or more.

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