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Please write a Python program to create a histogram. It must read text from stdin and output text to stdout. One line of output will correspond with one line of input. Each line of input will be two fields separated by a space. The first field will be a text label. The 2nd will be a numeric value. The output will be a histogram made out of ascii text characters. Each line will be the text label read as the first input field of each line followed by a bar the length of which will be proportional to the value of the 2nd field of input.

Here is a Python program that creates a histogram from input read from stdin and outputs it to stdout:


import sys

data = {}

for line in sys.stdin:
    label, value = line.strip().split()
    data[label] = int(value)

maximum = max(data.values())

for label, value in data.items():
    print(label + ": " + "*" * (value * 20 // maximum))

This program reads each line of input from stdin, and uses the strip() and split() methods to extract the label and value. It stores the data in a dictionary, with the label as the key and the value as the value.

Then it finds the maximum value in the data and uses this value to scale the values for the histogram. It then iterates through the data, printing the label, a colon and space, and the number of asterisks corresponding to the value (scaled by dividing it by the maximum value and multiplying by 20).

You can modify the code to change the character used to create the histogram.

OK, that's great. Two enhancements, please. (1) The left side of the histogram bars need to be aligned. (2) The longest length of any output line must be 80 characters. Please adjust the length of the bars so that they remain in proportion and the longest line is that length.

Here is an updated version of the Python program that creates a histogram with left-aligned bars and ensures that the longest output line is 80 characters:


import sys

data = {}

for line in sys.stdin:
    label, value = line.strip().split()
    data[label] = int(value)

maximum = max(data.values())

# Find the longest label length
max_label_length = max(len(label) for label in data)

# Scale the values so that the longest bar is 80 characters
scaling_factor = (80 - max_label_length - 2) / maximum

for label, value in data.items():
    print("{:<{width}}: {}".format(label, "*" * int(value * scaling_factor), width=max_label_length))

This program first finds the maximum value in the data, and then finds the length of the longest label. Then it calculates the scaling factor by dividing the difference between the desired output line length (80 characters) and the longest label length by the maximum value.

Then, it iterates through the data, printing the label left-aligned using the format() method, a colon and space, and the number of asterisks corresponding to the value (scaled by multiplying it by the scaling factor)

You can adjust the desired output length by modifying the value assigned to max_label_length

That's exactly what I asked for, thank you. But a better way of adjusting the desired output length would be to modify the hard coded constant 80.

You are correct, a better way to adjust the desired output length would be to use a variable instead of a hard-coded constant. Here is the updated version of the code where you can modify the desired output length by adjusting the value assigned to the max_output_length variable:


import sys

data = {}

for line in sys.stdin:
    label, value = line.strip().split()
    data[label] = int(value)

maximum = max(data.values())

# Find the longest label length
max_label_length = max(len(label) for label in data)

# Desired output length
max_output_length = 80

# Scale the values so that the longest bar is max_output_length characters
scaling_factor = (max_output_length - max_label_length - 2) / maximum

for label, value in data.items():
    print("{:<{width}}: {}".format(label, "*" * int(value * scaling_factor), width=max_label_length))

You can change the value of max_output_length to any other value, this way the program will adjust the output length accordingly.

It's my fault as you just follow my initial lead, but I think the program would be more readable if we didn't use both "width" and "length" as part of the variable names for (parts of the) the width of the output.

You are correct, using consistent variable names can make the code more readable. Here is an updated version of the code where I have replaced the "max_label_length" variable with "label_width" and "max_output_length" with "output_width":


import sys

data = {}

for line in sys.stdin:
    label, value = line.strip().split()
    data[label] = int(value)

maximum = max(data.values())

# Find the width of the longest label 
label_width = max(len(label) for label in data)

# Desired output width
output_width = 80

# Scale the values so that the longest bar is max_output_length characters
scaling_factor = (output_width - label_width - 2) / maximum

for label, value in data.items():
    print("{:<{width}}: {}".format(label, "*" * int(value * scaling_factor), width=label_width))

As you can see, I've changed the name of the variables to "label_width" and "output_width" respectively, this way the code is more readable and clear for the reader.

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