SymPy中如何美化输出到文件？及宽度限制问题解决

1. Why the Width Limit Exists & How to Fix It #

SymPy’s pprint (pretty printer) uses a default column width (typically 79 characters) by design—this is a legacy setting to ensure output fits in standard terminal windows and maintains readability across different systems. It doesn’t automatically detect your terminal’s current width unless you explicitly configure it.

Fixes: #

• Adjust width per pprint call: Pass the width parameter directly to pprint with your desired column count:

  sp.pprint(a, width=150)  # Use any width that fits your window
  

• Set global width for all prints: Use init_printing at the start of your script to configure the default width for all subsequent pretty prints:

  import sympy as sp
  from sympy.physics.quantum import TensorProduct
  
  sp.init_printing(width=150)  # Global width setting
  s = sp.eye(2)
  a = TensorProduct(s*x, TensorProduct(s,s)).subs(x, x**2+2*x+1)
  sp.pprint(a)
  

• Modify the printer’s global default: If you need even more control, you can adjust the base Printer class’s width:

  sp.printing.printer.Printer().width = 150
  

2. Printing Output to a File #

You have two straightforward ways to save the pretty-printed output to a file:

Method 1: Use the file parameter in pprint #

Open a file in write mode and pass it to the file argument of pprint. This works just like printing to the console but directs output to your file:

import sympy as sp
from sympy.physics.quantum import TensorProduct

s = sp.eye(2)
a = TensorProduct(s*x, TensorProduct(s,s)).subs(x, x**2+2*x+1)

# Write to file with custom width
with open('sympy_output.txt', 'w') as output_file:
    sp.pprint(a, width=150, file=output_file)

Method 2: Generate a pretty string and write it manually #

If you want to process the output string before saving, use sp.pretty() to get the formatted string, then write it to the file:

pretty_str = sp.pretty(a, width=150)
with open('sympy_output.txt', 'w') as output_file:
    output_file.write(pretty_str)

Both methods will save the properly formatted tensor product to your specified file with the width you set.

内容的提问来源于stack exchange，提问作者Xiaoyu Liu