Today's lab looks at loops for processing data from files.

### Social Security Administration Name Data

The Social Security Administration maintains lists of baby names indexed by state and year. Each of these files have the same format: on each line there is two characters for the state, followed by 'M' or 'F' for gender, the year, the name, and then the number of babies given that name that year. For example,
``` NYM1910Herbert,83
NYM1910Leo,80
NYM1910Andrew,79
NYM1910Ernest,79
NYM1910Milton,79
```
is part of the file NY.TXT containing the data for New York State. Note that in 1910, there were 83 boys named Herbert, 80 boys named Leo, and 79 boys eached named Andrew, Ernest, and Milton.

We are going to write a program that asks the user for a first name, and then reports back the average number of times that name occurs per year as well as the maximum number it occurs (and that year).

Here is a sample run of our program:

```Please enter the file name: NY.txt
Please enter the first name: Herbert
Herbert averaged 241.19 times per year.
It was most popular in 1929 occurring 928 times.
```
and another:
```Please enter the file name: NY.txt
Please enter the first name: Katherine
Katherine averaged 456.35 times per year.
It was most popular in 1990 occurring 978 times.
```
Our program encapsulates several important concepts:
• It reads through each line of the file, gathering several different data points from each line.
• It keeps both a running total as well as a running maximum of the data seen.
• After all the data has been processed, it calculates ending values ("post-processes") for the data.
• It formats the output for increased readability of the user.
Let's work through the program step-by-step: First, since we're going to calculate an average, we need to have variables to hold the total as well as the number of times they occur. We set those to 0 to start:
```#Lab:  calculating popularity of names in SSA data

def main():
#Set the totals to 0 to start:
total, numTimes = 0,0
```
We're also interested in the maximum number of times a name occurs and the year, so, we set those to 0 at the start:
```    #Set the max's to 0 to start:
maxOccur,maxYear = 0,0
```
Next, we ask the user for a file name and open the file:
```    fname = input("Please enter the file name: ")
infile = open(fname, "r")
```
And ask the user for the name to search for:
```    #Name we're searching for in the file:
searchee = input("Please enter the first name: ")
```
After we have finished with this initialization, we can now traverse the file. We will go line-by-line (storing the lines in the variable l):
```    for l in infile.readlines():
#The year always occurs in positions [4,8]:
year = eval(l[4:8])

#Split the rest of the line on the comma:
w = l[8:].split(",")

#w has the name, followed by the occurrences:
name = w
occur = eval(w)

#Check if the current name is the searchee and update:
if name == searchee:
total = total + occur
numTimes += 1
if occur > maxOccur:
maxOccur = occur
maxYear = year
```
The loop will finish when there are no more lines in the file. So, at the end of the loop, maxOccur and maxYear will hold the largest number of times the name occurred and the year, respectively. Similarly, total and numTimes will have the total number of New Yorkers given that name as well as the number of years in which the name was given. We can then use this information to calculate the average, and print out the maximums:
```    #Calculate the average and print out the collected data, nicely formatted:
average = total/numTimes
print(searchee, "averaged {0:0.02f} times per year.".format(average))
print("It was most popular in", maxYear, "occurring", maxOccur, "times.")
```
Try running the program (complete version below). If the name does not occur, what happens? Why? Think about ways to fix this to make it more user-friendly.

### The Complete Program

```#Lab:  calculating popularity of names in SSA data

def main():
#Set the totals to 0 to start:
total, numTimes = 0,0

#Set the max's to 0 to start:
maxOccur,maxYear = 0,0

fname = input("Please enter the file name: ")
infile = open(fname, "r")

#Name we're searching for in the file:
searchee = input("Please enter the first name: ")

#The year always occurs in positions [4,8]:
year = eval(l[4:8])

#Split the rest of the line on the comma:
w = l[8:].split(",")

#w has the name, followed by the occurrences:
name = w
occur = eval(w)

#Check if the current name is the searchee and update:
if name == searchee:
total = total + occur
numTimes += 1
if occur > maxOccur:
maxOccur = occur
maxYear = year

#Calculate the average and print out the collected data, nicely formatted:
average = total/numTimes
print(searchee, "averaged {0:0.02f} times per year.".format(average))
print("It was most popular in", maxYear, "occurring", maxOccur, "times.")

main()

```

If you finish early, you may work on the programming problems.